Method for preparing SSZ-39 molecular sieve by taking A type molecular sieve as raw material and application of SSZ-39 molecular sieve

Abstract

The invention belongs to the technical field of zeolite molecular sieve synthesis, and discloses a method for preparing an SSZ-39 molecular sieve by taking an A-type molecular sieve as a raw material and application of the SSZ-39 molecular sieve, a four-membered ring and six-membered ring structural unit of the A-type molecular sieve is highly matched with a framework element of the SSZ-39 molecular sieve, and an industrial grade A-type molecular sieve is taken as a core silicon-aluminum source. A part of the amorphous silicon source is additionally added, so that the limitation that the silicon-aluminum ratio of the A type molecular sieve is too low and cannot meet the requirement of an SSZ-39 molecular sieve synthesis interval is overcome, sodium hydroxide, a template agent and a seed crystal are added to construct a gel system, and synthesis of the SSZ-39 molecular sieve is realized through crystallization treatment. After the SSZ-39 molecular sieve obtained by the green synthesis process is modified by copper, the SSZ-39 molecular sieve shows a wide active window (250-500 DEG C, NOx conversion rate gt; 90%), and a low-cost and high-stability synthesis scheme is provided for large-scale production of the high-performance SCR catalyst.

Description

Technical Field

[0001] This application belongs to the technical field of zeolite molecular sieve synthesis, and specifically relates to a method for preparing SSZ-39 molecular sieve using A-type molecular sieve as raw material and its application. Background Art

[0002] The emission of nitrogen oxides (NO x ) in diesel engine exhaust is an important inducement for haze and photochemical pollution. Developing efficient purification technologies is of strategic significance for achieving the "dual carbon" goal. Ammonia selective catalytic reduction (NH3-SCR), as the most mature NO x post-treatment technology, the performance of its catalyst directly determines the system efficiency. Although the Cu-SSZ-13 molecular sieve with CHA structure has been commercially applied, its narrow active temperature window (200 - 450 °C) is difficult to meet the requirements of the National VI / Euro VII standards for high-efficiency denitrification in a wide temperature range. In 2012, Moliner et al. first reported that the Cu-SSZ-39 molecular sieve with AEI topological structure showed breakthrough advantages in the NH3-SCR reaction: the active window was extended to 200 - 600 °C; more than 90% of the NOx conversion rate was still maintained after hydrothermal aging at 800 °C (J. Am. Chem. Soc. 2012, 134, 6473 - 6476). This discovery has triggered an urgent need for the synthesis technology of SSZ-39 molecular sieve.

[0003] At present, the industrial sector mainly synthesizes SSZ-39 zeolite through the interzeolite topotactic transformation method, but its technical route has significant limitations. Usually, FAU zeolite (USY / HSY type) is used as the silicon-aluminum source, and SSZ-39 is synthesized through interzeolite transformation. Patent CN114988468A uses high-silica Y zeolite (HSY) as the raw material and tetraethylammonium hydroxide (TEAOH) as the templating agent to synthesize SSZ-39 zeolite through dynamic hydrothermal crystallization. However, the HSY raw material used in this method needs to be prepared by multiple steps of dealumination of low-silica Y zeolite (LSY) through steam treatment and pickling, and the dosage of the TEAOH templating agent is relatively high. After high-temperature calcination, nitrogen-containing waste gas is generated, which has an adverse impact on the environment. Patent CN115893445A adopts a dual-templating agent strategy of using low-cost amines and conventional templating agents together to synthesize SSZ-39 zeolite with ultrastable Y zeolite (USY) as the aluminum source. However, the preparation of USY requires high-temperature steam dealumination at 700 °C and pickling treatment, with prominent energy consumption and pollution problems, and the regulation of the dual-templating agent system is more difficult than that of a single templating agent. Patent CN115893445B uses a dual-templating agent strategy with USY, ZSM-5 or Beta zeolite as the aluminum source for re-alumination. Although the cost of the templating agent is reduced, relatively expensive zeolite aluminum sources are still required, and the dual-templating agent ratio window is narrow. Patent CN116040646A uses X zeolite (FAU type) as the raw material and combines a small amount of templating agent N,N-diethyl-2,6-dimethylpiperidinium salt to synthesize SSZ-39 zeolite through hydrothermal topotactic transformation, but the use of FAU type zeolite is still not avoided.

[0004] In addition to interzeolite transformation, in order to solve the problem of high energy consumption cost in the traditional preparation method of SSZ-39 zeolite, Xiao et al. from Zhejiang University first proposed to use conventional silica sol as the silicon source and sodium aluminate as the aluminum source instead of FAU type zeolite to achieve the synthesis of SSZ-39 zeolite. However, limited by the chemical conditions of the gel, the interval for synthesizing pure-phase SSZ-39 zeolite by this method is narrow, and the product is always accompanied by zeolite heterophases with structures such as MOR and ANA, requiring harsh conditions for control and high difficulty in large-scale production. (ACS Appl. Mater. Interfaces 2019, 11, 23112 - 23117). Patent CN106467306 discloses a method for synthesizing SSZ-39 zeolite in one step. Sodium silicate solution and sodium aluminate solution are mixed, and then N,N-dimethyl-2,6-dimethylpiperidinium templating agent is added. After aging at room temperature for 12 h to prepare a crystallization guiding agent, sodium silicate solution and aluminum sulfate solution are added to prepare an initial gel. Although expensive USY is not used in the synthesis, the steps for preparing the gel in this method are carried out in segments, with cumbersome steps and time-consuming, and low industrial efficiency.

[0005] In summary, considering the excellent performance of SSZ-39 zeolite in the NH3-SCR reaction, the existing methods for preparing SSZ-39 zeolite still have problems such as strong dependence on FAU-type zeolite raw materials, complex processes, and insufficient economy. Therefore, developing a synthesis method for SSZ-39 zeolite with inexpensive and easily available raw materials, a green and simple process, and adjustable product properties has become a technical problem that urgently needs to be solved in the field of diesel vehicle exhaust purification. Summary of the Invention

[0006] In view of the problems in the existing SSZ-39 zeolite synthesis technology, such as high synthesis cost and cumbersome synthesis process, the present invention first proposes a method and application for preparing SSZ-39 zeolite using A-type zeolite as a raw material. It is a green synthesis process for preparing SSZ-39 zeolite (AEI structure) by the transformation of A-type zeolite (LTA structure) and its catalytic application. As a mature adsorbent, the annual global production capacity of A-type zeolite exceeds one million tons, and its market price is only 1 / 5 - 1 / 3 of USY. It can be directly used as a silica-alumina source without complex pretreatment. Utilizing the topological structure similarity between the four- and six-membered ring units of A-type zeolite and the double six-membered ring framework of SSZ-39, the template agent can efficiently guide the framework reconstruction in a targeted manner, avoiding the structural dependence on FAU-type zeolite. The silicon-aluminum ratio (Si / Al = 8 - 15) of the obtained SSZ-39 zeolite can be precisely regulated to adapt to the catalytic requirements of NH3-SCR, providing a high-cost-effective solution for the diesel vehicle exhaust purification system.

[0007] The present invention adopts the following technical solutions:

[0008] A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material, comprising the following steps:

[0009] (1) Mix and stir the template agent, A-type zeolite, alkali source, part of the silicon source, and water, stir evenly, and then add SSZ-39 zeolite seeds, and stir evenly to obtain an initial gel;

[0010] (2) Load the initial gel obtained in step (1) into a reaction kettle, carry out crystallization treatment, and obtain the product Na-type SSZ-39 zeolite through filtration, washing, drying, and calcination;

[0011] In step (1), the molar ratio of the active components SiO2, Al2O3, alkali source, template agent, and H2O in the initial gel is 1:(0.01 - 0.10):(0.10 - 0.60):(0.10 - 0.50):(5 - 30), where the active component SiO2 is derived from A-type zeolite and part of the silicon source.

[0012] Furthermore, the initial gel in step (1) further includes a crystallization regulator, and the molar ratio of the crystallization regulator to SiO2 is 0.001 - 0.10.

[0013] Further, the crystallization regulator includes at least one of malic acid, lactic acid, ethylenediaminetetraacetic acid, glucose, oxalic acid, tartaric acid, citric acid, and lactic acid.

[0014] Further, the template agent includes one or more of N,N-dimethyl-2,6-dimethylpiperidinium hydroxide, N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2-ethylpiperidinium hydroxide, N-ethyl-N-methyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-2,2-dimethyl-2,5-dihydropyrrole cationic compound, N,N-dimethyl-9-azoniabicyclononane compound, and 2,2,4,6,6-pentamethylene-2-azoniabicyclooctane compound. Further still, the template agent is N,N-dimethyl-3,5-dimethylpiperidinium hydroxide.

[0015] Further, the type A molecular sieve is selected from HA type zeolite or NaA type zeolite, and the molar ratio of its silicon-aluminum oxide ≤ 3.

[0016] Further, in step (1), the addition amount of the SSZ-39 zeolite seed is 2-10% of the sum of the solid masses of the effective silicon source (SiO2) and the effective aluminum source (Al2O3) (the sum of the solid silica mass in part of the silicon source and the mass of the type A molecular sieve).

[0017] Further, the part of the silicon source includes one or more of silica sol, solid silica gel, water glass, sodium silicate, tetraethyl orthosilicate, and precipitated silica.

[0018] Further, the part of the silicon source includes silica sol, and the mass fraction of the silica sol is 25-35%, and further preferably 30%.

[0019] Further, the alkali source includes sodium hydroxide and / or potassium hydroxide.

[0020] Further, in step (2), the temperature of the crystallization treatment is 120-200 °C, and the time of the crystallization treatment is 4-96 h.

[0021] Further, it also includes performing ammonium exchange on the Na type SSZ-39 zeolite with an ammonium salt aqueous solution, and then filtering, washing, drying, and calcining to obtain the H type SSZ-39 zeolite.

[0022] Further, the concentration of the ammonium salt aqueous solution is 0.2-1 M, and the ammonium exchange temperature is 40-80 °C.

[0023] Further, the number of exchange times is 1-3 times, and the ammonium salt is ammonium chloride or ammonium nitrate.

[0024] Further, the mass-volume ratio of the Na-type SSZ-39 molecular sieve to the ammonium salt aqueous solution is 1:10 to 15 g / ml.

[0025] Further, the calcination temperature is 400 to 540 °C, and the calcination time is 5 to 12 h.

[0026] Further, the drying temperature is 80 to 110 °C, and the drying time is 12 to 24 h.

[0027] According to the second aspect of the present application, a method for preparing a Cu-SSZ-39 catalyst is provided, which includes modifying the H-type SSZ-39 molecular sieve in a copper salt solution to obtain a Cu-SSZ-39 catalyst.

[0028] The mass fraction of copper in the Cu-SSZ-39 catalyst is 1.05% to 3.10%. The copper salt is copper acetate.

[0029] The preparation method of the Cu-SSZ-39 catalyst specifically includes adding the H-type SSZ-39 molecular sieve to a 0.05 to 0.1 mol / L copper acetate solution for ion exchange for 300 to 360 min under stirring conditions at 50 to 80 °C, with a liquid-solid ratio of 1:3 to 5. After suction filtration and washing, drying at 80 to 110 °C for 12 to 24 h, and calcining at 540 °C to 600 °C for 6 to 12 h to obtain the Cu-SSZ-39 molecular sieve.

[0030] According to the third method of the present application, the application of the Cu-SSZ-39 catalyst obtained by the method in automotive exhaust denitrification is provided.

[0031] In the present invention, unless otherwise specified, the numerical range refers to any value within the range and includes the endpoint values.

[0032] The beneficial effects of the present invention include: breaking through the path dependence on FAU-type molecular sieves in traditional technologies, using inexpensive and easily available A-type molecular sieves (LTA type) as all aluminum sources and part of the silicon sources, and realizing the simple and efficient synthesis of SSZ-39 molecular sieves (AEI structure) through crystal transformation. After the obtained SSZ-39 molecular sieve is ion-exchanged with copper ions, it shows an ultra-wide activity window in the NH3-SCR reaction: when the temperature is 250 - 500 °C, the NOx conversion rate > 90% (space velocity 600000 h -1 ). It has important application value in the field of diesel vehicle exhaust treatment. Description of the Drawings

[0033] Figure 1 It is an X-ray diffraction (XRD) test diagram of the sample prepared in Comparative Example 1.

[0034] Figure 2These are X-ray diffraction (XRD) test diagrams of the samples prepared in Examples 1-8 of the present invention.

[0035] Figure 3 The nitrogen physical adsorption curves and pore size distribution diagrams of the samples prepared in Examples 1-8 of the present invention and the samples prepared in Comparative Examples 1-2 are shown.

[0036] Figure 4 This is a tungsten filament scanning electron microscope (SEM) test image of the sample prepared in Example 1 of the present invention.

[0037] Figure 5 NH3-SCR reaction test diagram of the samples prepared in Comparative Example 1 and Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0038] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0039] Unless otherwise specified, the raw materials in the examples of this application are purchased from commercial sources. The SSZ-39 zeolite molecular sieve used as the seed crystal comes from a purchased commercial product, and its oxide silicon-aluminum ratio is 20. Unless otherwise specified, the analysis methods in the examples all adopt the conventional settings of the instrument and conventional analysis methods.

[0040] The analysis method in the examples of this application is as follows:

[0041] X-ray diffraction (XRD) analysis of catalytic samples: XRD characterization was performed using a Rigaku X-ray powder diffractometer (model: Rigaku Smartlab 9) from Japan.

[0042] The analysis conditions were CuKα target (λ=0.1548 nm), Ni filter, tube voltage 40 kV, tube current 100 mA, scanning range 2θ angle 5°~40°, scanning rate 8° / min.

[0043] Nitrogen physical adsorption characterization of samples: The catalyst was characterized by nitrogen physical adsorption on the JW-BK200 surface and pore size analyzer produced by Beijing Jingwei Gaobo Science and Technology Co., Ltd. 150 mg of sample was pretreated at 300 ° C under vacuum conditions for 2 hours, and then measured with N2 as the adsorbent. The total specific surface area of the catalyst was calculated using the BET equation, and the total pore volume was obtained when the relative pressure p / p0 = 0.99. The micropore specific surface area and pore volume were obtained using the t-plot method.

[0044] Tungsten filament scanning electron microscope (SEM) test of the sample: Scanning electron microscope (SEM) images were obtained under a SU8220 microscope from Rigaku Corporation of Japan to observe the morphology of the prepared molecular sieve.

[0045] The denitrification performance of the catalyst was evaluated by the following method: 0.07 g (20-40 mesh) of the catalyst, [NO]=[NH3]=0.5%, [O2]=20%, N2 was used as the balance gas, and GHSV=600000 h- 1 .

[0046] Among them, GHSV is the abbreviation of gas hourly space velocity, that is: gas hourly space velocity.

[0047] Among them, NO x Conversion rate = (1 - [NO] 出口 / [NO] 入口 ) × 100%

[0048] In this application, the dehydration pretreatment of the zeolite molecular sieve adopts the conventional drying or calcination method. In the examples, the dehydration pretreatment of the zeolite molecular sieve is carried out according to the following method: the zeolite molecular sieve is put into a muffle furnace, and the temperature is raised from room temperature to 540 °C for 2 hours and then calcined for 3 hours.

[0049] Comparative Example 1

[0050] (1) The Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) were subjected to calcination for water removal pretreatment;

[0051] (2) 45 g of deionized water, 1.10 g of sodium hydroxide, 4.20 g of USY molecular sieve (SiO2 / Al2O3 = 40), and 12.18 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) were stirred at room temperature for 2 h until homogeneous, and then 0.08 g of the Na-SSZ-39 seeds pretreated in step (1) (seed amount / solid mass equal to 2%) was added, and after stirring for 10 min, an initial gel was obtained;

[0052] (3) The initial gel obtained in step (2) was placed in a hydrothermal autoclave, and then the reaction kettle was placed in an oven for crystallization treatment at 150 °C for 72 h;

[0053] (4) After the crystallization in step (3) was completed, the crystallization product was filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace, and the temperature was programmed to 600 °C and calcined in an air stream for 12 h to obtain the Na-type molecular sieve.

[0054] (5) The Na-type molecular sieve obtained in step (4) was exchanged 3 times with a 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace, and the temperature was programmed to 600 °C and calcined in an air stream for 6 h to obtain the H-type molecular sieve.

[0055] The sample obtained in this example is denoted as sample D1#. Its XRD pattern is shown in Figure 1 , and the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (i). The silicon-aluminum ratio of the product measured by XRF characterization is 14.4.

[0056] Example 1

[0057] (1) Pre-treat the Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) by calcination to remove water.

[0058] (2) After stirring 0.73 g of sodium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO2 / Al2O3 = 2), and 12.00 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, add 0.08 g of anhydrous glucose and stir for 1 h until homogeneous, then add 0.08 g of the Na-SSZ-39 seeds pretreated in step (1) (the amount of seeds / solid mass is equal to 2%), and stir for 10 min to obtain the initial gel; the solid mass is the sum of the masses of the effective silicon source (SiO2) and the effective aluminum source (Al2O3).

[0059] (3) Place the initial gel obtained in step (2) in a hydrothermal autoclave, and then place the reaction kettle in an oven for crystallization treatment at 150 °C for 72 h.

[0060] (4) After the crystallization in step (3) is completed, the crystallized product is filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace, and the temperature is programmed to 600 °C and calcined in an air stream for 12 h to obtain the Na-type molecular sieve.

[0061] (5) Exchange the Na-type molecular sieve obtained in step (4) three times with 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filter, wash, place in an oven and dry at 110 °C, and then place in a muffle furnace, and the temperature is programmed to 600 °C and calcined in an air stream for 6 h to obtain the H-type molecular sieve.

[0062] The sample obtained in this example is denoted as sample 1#. Its XRD pattern is shown in Figure 2 , and the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (a), the SEM image is shown in Figure 4 , and the silicon-aluminum ratio of the product measured by XRF characterization is 9.1.

[0063] Example 2

[0064] (1) Pre-treat the Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) by calcination to remove water.

[0065] (2) After stirring 0.80 g of sodium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO₂ / Al₂O₃ = 2), and 12.85 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, 0.08 g of the Na-SSZ-39 seed crystals pretreated in step (1) (seed crystal amount / solid mass equal to 2%) was added, and after stirring for 10 min, an initial gel was obtained;

[0066] (3) The initial gel obtained in step (2) was placed in a hydrothermal autoclave, and then the reaction kettle was placed in an oven for crystallization treatment at 150 °C for 72 h;

[0067] (4) After the crystallization in step (3) was completed, the crystallization product was filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace. The temperature was programmed to 600 °C and calcined in an air stream for 12 h to obtain a Na-type molecular sieve.

[0068] (5) The Na-type molecular sieve obtained in step (4) was exchanged 3 times with 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace. The temperature was programmed to 600 °C and calcined in an air stream for 6 h to obtain an H-type molecular sieve.

[0069] The sample obtained in this example was denoted as sample 2#. Its XRD pattern is shown in Figure 2 , and the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (b). The silicon-aluminum ratio of the product measured by XRF characterization was 8.2.

[0070] Example 3

[0071] (1) The Na-SSZ-39 molecular sieve seed crystals (SiO₂ / Al₂O₃ = 20) were pretreated by roasting to remove water;

[0072] (2) After stirring 1.08 g of sodium hydroxide, 11.88 g of silica sol (mass fraction 30%), 0.24 g of Na-A type molecular sieve (SiO₂ / Al₂O₃ = 2), and 9.76 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, 0.08 g of the Na-SSZ-39 seed crystals pretreated in step (1) (seed crystal amount / solid mass equal to 2%) was added, and after stirring for 10 min, an initial gel was obtained;

[0073] (3) The initial gel obtained in step (2) was placed in a hydrothermal autoclave, and then the reaction kettle was placed in an oven for crystallization treatment at 150 °C for 72 h;

[0074] (4) After the crystallization in step (3) is completed, the crystallization product is filtered, washed, dried in an oven at 110 °C, then placed in a muffle furnace, and the temperature is programmed to 600 °C for calcination in an air stream for 12 h to obtain Na-type molecular sieve.

[0075] (5) The Na-type molecular sieve obtained in step (4) is exchanged 3 times with 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, dried in an oven at 110 °C, and then placed in a muffle furnace, and the temperature is programmed to 600 °C for calcination in an air stream for 6 h to obtain H-type molecular sieve.

[0076] The sample obtained in this example is denoted as sample 3#. Its XRD pattern is shown in Figure 2 , the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (c), and the silicon-aluminum ratio of the product measured by XRF characterization is 14.4.

[0077] Example 4

[0078] (1) The Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) are pretreated by calcination to remove water.

[0079] (2) After stirring 1.06 g of sodium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO2 / Al2O3 = 2), and 12.00 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, 0.71 g of citric acid monohydrate is added and stirred for 1 h until homogeneous, and then 0.08 g of the Na-SSZ-39 seeds pretreated in step (1) (the amount of seeds / solid mass is equal to 2%) is added, and after stirring for 10 min, an initial gel is obtained.

[0080] (3) The initial gel obtained in step (2) is placed in a hydrothermal autoclave, and then the reaction kettle is placed in an oven for crystallization treatment at 150 °C for 72 h.

[0081] (4) After the crystallization in step (3) is completed, the crystallization product is filtered, washed, dried in an oven at 110 °C, then placed in a muffle furnace, and the temperature is programmed to 600 °C for calcination in an air stream for 12 h to obtain Na-type molecular sieve.

[0082] (5) The Na-type molecular sieve obtained in step (4) is exchanged 3 times with 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, dried in an oven at 110 °C, and then placed in a muffle furnace, and the temperature is programmed to 600 °C for calcination in an air stream for 6 h to obtain H-type molecular sieve.

[0083] The sample obtained in this example is denoted as sample 4#. Its XRD pattern is shown in Figure 2, the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (d), the silicon-aluminum ratio of the product measured by XRF characterization is, and the silicon-aluminum ratio of the product measured by XRF characterization is 9.6.

[0084] Example 5

[0085] (1) Pre-treat the Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) by calcination to remove water.

[0086] (2) After stirring 1.00 g of sodium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO2 / Al2O3 = 2), and 12.00 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, add 0.60 g of ethylenediaminetetraacetic acid and stir for 1 h until homogeneous, then add 0.08 g of the Na-SSZ-39 seeds pretreated in step (1) (the amount of seeds / solid mass is equal to 2%), and stir for 10 min to obtain the initial gel.

[0087] (3) Place the initial gel obtained in step (2) in a hydrothermal autoclave, and then place the reaction kettle in an oven for crystallization treatment at 150 °C for 72 h.

[0088] (4) After the crystallization in step (3) is completed, the crystallized product is filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace, and the temperature is programmed to 600 °C and calcined in an air stream for 12 h to obtain the Na-type molecular sieve.

[0089] (5) Exchange the Na-type molecular sieve obtained in step (4) with 0.4 M ammonium nitrate solution 3 times at an exchange temperature of 50 °C, then filter, wash, place in an oven and dry at 110 °C, and then place in a muffle furnace, and the temperature is programmed to 600 °C and calcined in an air stream for 6 h to obtain the H-type molecular sieve.

[0090] The sample obtained in this example is denoted as sample 5#. Its XRD pattern is shown in Figure 2 , the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (e), the silicon-aluminum ratio of the product measured by XRF characterization is 9.2.

[0091] Example 6

[0092] (1) Pre-treat the Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) by calcination to remove water.

[0093] (2) After stirring 1.06 g of sodium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO2 / Al2O3 = 2), and 12.00 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, 0.71 g of tartaric acid was added and stirred for 1 h until homogeneous, and then 0.08 g of the Na-SSZ-39 seed crystals pretreated in step (1) (seed crystal amount / solid mass equal to 2%) was added. After stirring for 10 min, an initial gel was obtained;

[0094] (3) The initial gel obtained in step (2) was placed in a hydrothermal autoclave, and then the reaction kettle was placed in an oven for crystallization treatment at 150 °C for 72 h;

[0095] (4) After the crystallization in step (3) was completed, the crystallization product was filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace. The temperature was programmed to 600 °C and calcined in an air stream for 12 h to obtain a Na-type molecular sieve.

[0096] (5) The Na-type molecular sieve obtained in step (4) was exchanged 3 times with a 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, placed in an oven and dried at 110 °C, and then placed in a muffle furnace. The temperature was programmed to 600 °C and calcined in an air stream for 6 h to obtain an H-type molecular sieve.

[0097] The sample obtained in this example was designated as sample 6#. Its XRD pattern is shown in Figure 2 , and the nitrogen physical adsorption curve and pore size distribution diagram are shown in Figure 3 (f). The silicon-aluminum ratio of the product measured by XRF characterization was 10.2.

[0098] Example 7

[0099] (1) The Na-SSZ-39 molecular sieve seeds (SiO2 / Al2O3 = 20) were pretreated by roasting to remove water;

[0100] (2) After stirring 1.00 g of sodium hydroxide, 0.22 g of potassium hydroxide, 12.73 g of silica sol (mass fraction 30%), 0.50 g of Na-A type molecular sieve (SiO2 / Al2O3 = 2), and 5.58 g of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (mass fraction 25%) at room temperature for 2 h, 0.08 g of the Na-SSZ-39 seed crystals pretreated in step (1) (seed crystal amount / solid mass equal to 2%) was added. After stirring for 10 min, an initial gel was obtained;

[0101] (3) The initial gel obtained in step (2) was placed in a hydrothermal autoclave, and then the reaction kettle was placed in an oven for crystallization treatment at 150 °C for 72 h;

[0102] (4) After the crystallization in step (3) is completed, the crystallization product is filtered, washed, dried in an oven at 110 °C, and then placed in a muffle furnace. The temperature is programmed to rise to 600 °C and calcined in an air stream for 12 h to obtain Na-type zeolite molecular sieve.

[0103] (5) The Na-type zeolite molecular sieve obtained in step (4) is exchanged 3 times with 0.4 M ammonium nitrate solution at an exchange temperature of 50 °C, then filtered, washed, dried in an oven at 110 °C, and then placed in a muffle furnace. The temperature is programmed to rise to 600 °C and calcined in an air stream for 6 h to obtain H-type zeolite molecular sieve.

[0104] The sample obtained in this example is denoted as sample 7#. Its XRD pattern is shown in Figure 2 , and the nitrogen physical adsorption curve and pore size distribution map are shown in Figure 3 (g). The silicon-aluminum ratio of the product measured by XRF characterization is 10.8.

[0105] Example 8

[0106] The operation is the same as that in Example 2, except that only the crystallization temperature is changed, and the crystallization temperature is 170 °C.

[0107] The sample obtained in this example is denoted as sample 8#. Its XRD pattern is shown in Figure 1 , and the nitrogen physical adsorption curve and pore size distribution map are shown in Figure 3 (h). The silicon-aluminum ratio of the product measured by XRF characterization is 8.5.

[0108] Example 9

[0109] The samples prepared in the above examples were characterized by X-ray diffraction (XRD). Taking sample D1 and samples 1# to 8# as examples, their XRD patterns are respectively as Figure 1 and Figure 2 shown. The results show that samples 1# to 8# all exhibit the characteristic diffraction peaks of SSZ-39 zeolite molecular sieve, indicating that these samples have all been successfully synthesized with SSZ-39 zeolite molecular sieve. The relative crystallinity data are shown in Table 1.

[0110] Among samples 1# to 8#, sample 1# and samples 4# - 6# respectively represent the SSZ-39 zeolite molecular sieve products synthesized by adding crystallization regulators glucose, citric acid, ethylenediaminetetraacetic acid, and tartaric acid when the feed silicon-aluminum ratio (SiO2 / Al2O3) is 40. Samples 2# and 3# respectively represent the products synthesized when the feed silicon-aluminum ratio is 40 and 80 without adding crystallization regulators. Among them, sample 1# with added glucose and sample 3# with a feed silicon-aluminum ratio of 80 have the highest relative crystallinity. Sample 7# changes the alkali source and uses a mixture of sodium hydroxide and potassium hydroxide as the alkali source. At K +Under the structure guiding effect, the dosage of expensive and toxic templating agent is significantly reduced by more than 50%. Sample D1# was synthesized by the traditional method using USY molecular sieve as the silicon-aluminum source to synthesize SSZ-39 molecular sieve. Compared with Sample D1#, Samples 1# to 8# significantly reduce the synthesis raw material cost, and at the same time expand the synthesis path of SSZ-39 molecular sieve. The present invention synthesizes SSZ-39 molecular sieve by converting industrially cheap and easily available A-type molecular sieve, avoiding the dependence on expensive FAU-type molecular sieve raw materials in the traditional method, and by introducing K + , significantly reducing the dosage of the templating agent, thereby realizing the efficient and low-cost synthesis of SSZ-39 molecular sieve.

[0111] Example 10

[0112] The samples obtained from the above examples were characterized by nitrogen physical adsorption. Taking Samples 1# - 8# and Sample D1# as examples, the results are shown in Table 1 and Figure 3 (a)-(j). The nitrogen physical adsorption isotherms of all samples are of Type I, representing typical microporous structures. Sample 1# has the highest specific surface area and the largest total pore volume. The above results show that glucose as a crystallization regulator has an obvious effect on improving the microporous structure construction of the molecular sieve product.

[0113] Table 1 Nitrogen physical adsorption data of different samples

[0114]

[0115]

[0116] Test Example 1

[0117] The H-type SSZ-39 molecular sieves prepared in Examples 1 - 3 and Comparative Example 1 above were respectively modified with 0.10 mol / L copper acetate solution under stirring at 60 °C for 5 h, filtered, washed, dried at 110 °C for 12 h, and calcined at 540 °C for 6 h to obtain Cu-SSZ-39 molecular sieve. The prepared Cu-SSZ-39 was granulated to 20 - 40 mesh, and 0.07 g of the sample was tested for NH3-SCR reaction in a fixed-bed reactor. The reaction gas mixture composition was: 0.5% NO, 0.5% NH3, 20% O2, and the balance gas was N2. The space velocity was 600000 h -1 , the reaction temperature was 100 - 550 °C, and a laboratory self-built portable nitrogen oxide activity evaluation device was used to analyze the reaction outlet gas concentration. The reaction data is as Figure 5 and Table 2 show.

[0118] Table 2 NH3-SCR reaction data of Cu-SSZ-39 molecular sieve

[0119]

[0120] In summary, from the NH3-SCR reaction evaluation results, it can be seen that for the samples modified with Cu, in the temperature range of 250°C - 500°C, the NOx conversion rates of all samples in Example 1, Example 2, and Example 3 reached over 90%. Compared with sample D1# synthesized by the traditional USY conversion method in Comparative Example 1, all samples in samples 1# - 3# reached and even exceeded the NH3-SCR performance of sample D1# almost in the entire temperature window of 150°C - 550°C. Especially, sample 1# could still maintain a NO x conversion rate close to 90% at 550°C, indicating that the molecular sieve samples obtained by this invention showed excellent catalytic performance and high hydrothermal stability in the NH3-SCR reaction after Cu modification.

[0121] The above are only several embodiments of the present invention and do not impose any form of limitation on the present invention. Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the relevant art can make some changes or modifications within the scope of the technical solution of the present invention by using the disclosed technical content, and these are all equivalent to equivalent implementation cases and belong to the scope of the technical solution.

Claims

1. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material, characterized in that, It includes at least the following steps: S1 Mix the template agent, A-type molecular sieve, alkali source, partial silicon source and water evenly by stirring, and then add the SSZ-39 molecular sieve seeds and stir evenly to obtain an initial gel; S2 Load the initial gel into a reaction kettle for crystallization treatment, and obtain Na-type SSZ-39 molecular sieve through filtration, washing, drying and calcination; In step S1, the molar ratio of the effective components SiO2, Al2O3, alkali source, template agent, and H2O in the initial gel is 1:(0.01~0.10):(0.10~0.60):(0.10~0.50):(5~30).

2. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 1, characterized in that, The initial gel also includes a crystallization regulator, and the molar ratio of the crystallization regulator to SiO2 is 0.001~0.

10.

3. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 2, characterized in that, The crystallization regulator includes one or more of malic acid, lactic acid, ethylenediaminetetraacetic acid, glucose, oxalic acid, tartaric acid, citric acid and lactic acid.

4. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 1 or 2, characterized in that, The template agent includes at least one of N,N-dimethyl-2,6-dimethylpiperidinium hydroxide, N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2-ethylpiperidinium hydroxide, N-ethyl-N-methyl-2,6-dimethylpiperidinium hydroxide, N,N-diethyl-2,2-dimethyl-2,5-dihydropyrrole cationic compound, N,N-dimethyl-9-azoniabicyclononane compound, and 2,2,4,6,6-pentamethylene-2-azoniabicyclooctane compound.

5. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 1 or 2, characterized in that, The A-type molecular sieve is selected from HA-type molecular sieve or NaA-type molecular sieve, and the molar ratio of its silicon-aluminum oxide ≤ 3; and / or, The alkali source includes sodium hydroxide and / or potassium hydroxide; and / or, The partial silicon source includes one or more of water glass, sodium silicate, solid silica gel, silica sol, tetraethyl orthosilicate and precipitated silica.

6. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 1 or 2, characterized in that, The addition amount of the SSZ-39 molecular sieve seeds is 2~10% of the sum of the mass of solid silicon dioxide in the partial silicon source and the mass of the A-type molecular sieve; and / or, The crystallization temperature is 120~200 °C, and the crystallization time is 4~96 h.

7. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 1 or 2, characterized in that, It also includes subjecting the Na-type SSZ-39 molecular sieve to ammonium exchange with an ammonium salt aqueous solution, and then through filtration, washing, drying and calcination to obtain an H-type SSZ-39 molecular sieve.

8. A method for preparing SSZ-39 zeolite using A-type zeolite as a raw material according to claim 7, characterized in that, The concentration of the ammonium salt aqueous solution is 0.2~1 M, and the ammonium exchange temperature is 40~80 °C.

9. A preparation method of a Cu-SSZ-39 catalyst, characterized in that: It includes subjecting the H-type SSZ-39 molecular sieve obtained by the method according to claim 7 to ion exchange modification in a copper salt solution to obtain a Cu-SSZ-39 catalyst.

10. The application of the Cu-SSZ-39 catalyst obtained by the method according to claim 9 in automotive exhaust denitrification.

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