One-step transformation synthesis of Cu / rare earth-ssz-13 zeolite and preparation method and application thereof

Abstract

The application provides a preparation method of Cu / rare earth-SSZ-13 molecular sieve synthesized by one-step transformation of cheap zeolite and application thereof, and belongs to the technical field of molecular sieve synthesis. The preparation method is as follows: a complex of copper and tetraethylenepentamine (Cu-TEPA) and rare earth metals are dispersed in deionized water, and after uniform dispersion, cheap zeolite, a silicon source and crystal seeds are sequentially added, and after uniform stirring, an alkali source and N,N,N-trimethyladamantylammonium hydroxide are continuously added, so that an initial gel is finally obtained; after crystallization, washing, drying and calcination, the molecular sieve crude powder is obtained. The molecular sieve crude powder is applied to an ammonia selective catalytic reduction reaction after removal of excessive copper ions by ammonia exchange. In the application, copper ions and rare earth metal ions are introduced in one step, the crystallization time is shortened, the silicon-aluminum ratio of the product can be adjusted within a certain range, the Cu-SSZ-13 molecular sieve crystal formed has regular morphology, the solid-phase yield is high, there is no copper ion exchange post-processing step, and the generation of copper-containing wastewater is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a one-step transformation synthesis of Cu / rare earth-SSZ-13 molecular sieve from cheap zeolite and a preparation method and application thereof, and belongs to the technical field of molecular sieve synthesis. BACKGROUND

[0002] CHA type molecular sieve has orthorhombic symmetry, one-dimensional main channel is composed of double eight-membered rings, the pore size is 0.38 nm x 0.38 nm, and the framework density is 14.5; the CHA large cage formed by double six-membered rings (d6r) through four-membered ring connection has multiple sites for copper ion combination. As an important member in CHA structure, SSZ-13 molecular sieve has a large specific surface area, and has more proton acid centers and more exchangeable cation sites, so the molecular sieve exhibits excellent performance in diesel vehicle exhaust NO X removal, methanol to olefin and CO2 adsorption separation. Generally, the synthesis of SSZ-13 molecular sieve usually uses N,N,N-trimethyladamantylammonium hydroxide (TMAdaOH) as a template and uses amorphous silica-alumina source as a raw material for synthesis, but due to the reasons such as high price of N,N,N-trimethyladamantylammonium hydroxide (TMAdaOH) and large amount of template used, the industrialized production and application of SSZ-13 are limited.

[0003] The synthesis of SSZ-13 molecular sieves requires the use of amorphous silica-alumina sources and a large amount of N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), increasing both costs and carbon emissions. Some researchers have proposed an alternative, more efficient zeolite synthesis method—the transcrystalline method. This method uses one zeolite as a starting material to transform into another. Compared to conventional amorphous silica-alumina source synthesis methods, the transcrystalline zeolite decomposes / dissolves into fine structural units under the action of alkali. These structural units can then rapidly and selectively assemble into another zeolite under the action of a structure-directing agent. Compared to traditional amorphous gel synthesis, the transcrystalline method has attracted increasing attention due to its advantages of lower template agent usage, shorter reaction time, and higher yield. In recent years, due to its good hydrothermal stability, researchers have paid more attention to modified Cu-SSZ-13 molecular sieves. Chinese patent CN202110575336 discloses a method for synthesizing SSZ-13 by crystallization of A zeolite, with a template agent to SiO2 ratio of 0.03 to 0.1 and a hydrothermal reaction time of 8 to 16 hours. Chinese patent CN201910426727 discloses a method for Cu-SSZ-13 molecular sieve and its catalyst, using several quaternary ammonium bases to adjust the pH value of the system, with a template agent to Al2O3 ratio of 1 to 6 and a crystallization time of 24 to 120 hours. The above methods have the following problems: (1) the raw materials used are single and the crystallization reaction time is long; (2) the template agent N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH) is used in large quantities and the cost is high; (3) the selectivity of the ammonia selective catalytic reduction reaction is poor; (4) the post-treatment requires multiple steps of ion exchange to load metal, resulting in a large amount of wastewater, a large number of required equipment, and high energy consumption. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing Cu / rare earth-SSZ-13 molecular sieves via a one-step zeolite transformation and its application. This method is low-cost, requires few post-processing steps, and is environmentally friendly. The exchanged Cu / rare earth-SSZ-13 exhibits a wide temperature window when applied in NH3-SCR, which is of great significance for the industrial promotion of SSZ-13 molecular sieves.

[0005] This invention provides a method for synthesizing SSZ-13 molecular sieves in one step using several inexpensive and readily available zeolite raw materials, and applies it to the selective catalytic reduction reaction of ammonia (NH3-SCR). The preparation method is as follows:

[0006] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite includes the following steps:

[0007] A copper-tetraethylenepentamine complex (Cu-TEPA) and rare earth metals were dispersed in deionized water. After uniform dispersion, inexpensive zeolite, silicon source, and seed crystals were added sequentially. After stirring evenly, an alkali source and N,N,N-trimethyladamantyl ammonium hydroxide were added to obtain an initial gel. The initial gel was transferred to a high-pressure reactor lined with polytetrafluoroethylene for crystallization. The crystallized product was washed, dried, and calcined to obtain molecular sieve powder. The molecular sieve powder was subjected to ammonia exchange with an ammonia source to obtain rare earth metal modified Cu-SSZ-13 molecular sieve.

[0008] The inexpensive zeolite is one or more of the following: sodalite (SOD type structure), analcime (ANA type structure), X-type zeolite (FAU type structure), and A-type zeolite (LTA type structure); the molar ratio of silicon and aluminum oxide in the sodalite is 1-2.5:1; the molar ratio of silicon and aluminum oxide in the analcime is 3.6-5.6:1; the molar ratio of silicon and aluminum oxide in the X-type zeolite is 2.2-3:1; and the molar ratio of silicon and aluminum oxide in the A-type zeolite is 1.8-2.5:1.

[0009] Furthermore, the method includes the following steps:

[0010] Step 1: Disperse the copper-tetraethylenepentamine complex (Cu-TEPA) and rare earth metals in deionized water. After uniform dispersion, add inexpensive zeolite, silicon source and seed crystals in sequence. After stirring evenly, add alkali source and N,N,N-trimethyladamantyl ammonium hydroxide to finally obtain the initial gel.

[0011] Step 2: Transfer the initial gel obtained in Step 1 to a high-pressure reactor lined with stainless steel and polytetrafluoroethylene for crystallization.

[0012] Step 3: Wash, dry, and calcine the crystallized product obtained in Step 2 to obtain molecular sieve raw powder. After ammonia exchange with an ammonia source, the raw powder is used to obtain Cu-SSZ-13 molecular sieve modified with rare earth metal.

[0013] Furthermore, the molar ratio of the materials in the initial gel is: xAl2O3:SiO2:yM2O:zR:aCu-TEPA:bH2O, where x = 0.04–0.14, y = 0.25–1, z = 0.01–0.03, a = 0.05–0.3, and b = 15–60. Wherein, M is the alkali metal ion in the alkali source, R is N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), Cu-TEPA is a copper-tetraethylenepentamine complex, the molar ratio of copper to tetraethylenepentamine (TEPA) is 1:1, the mass of the seed crystal is 1%–5% of the sum of the solid masses of the inexpensive zeolite and the silicon source, and the mass of the rare earth metal salt is 1%–10% of the sum of the solid masses of the inexpensive zeolite and the silicon source.

[0014] Furthermore, the silicon source is used to adjust the silicon-to-aluminum ratio and is one or more of silica sol, silica fume, and silicon powder.

[0015] Furthermore, the alkali source is one or both of sodium hydroxide and potassium hydroxide.

[0016] Furthermore, the copper source in the copper-tetraethylenepentamine complex is one or more of copper sulfate, copper nitrate, and copper acetate.

[0017] The seed crystal is SSZ-13 molecular sieve.

[0018] The rare earth metal salt contains one or two rare earth elements, namely lanthanum and cerium, and its source is one or more of the corresponding rare earth nitrates, rare earth acetates and rare earth chlorides.

[0019] The crystallization temperature in step two is 140℃~200℃, and the crystallization time is 8~20h.

[0020] The drying temperature in step three is 120℃, and the drying time is 12 hours. The calcination temperature is 550℃, and the calcination time is 5 hours.

[0021] The ammonia source in the ammonia exchange described in step three is one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, and ammonium bicarbonate, and the exchange temperature is 40℃~90℃.

[0022] The present invention also provides a molecular sieve prepared by the above method.

[0023] The present invention also provides the application of the above-mentioned molecular sieve in the selective catalytic reduction reaction of ammonia (NH3-SCR).

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The silicon-aluminum source used in this invention is inexpensive and readily available zeolite, which is low in cost and environmentally friendly. An additional silicon source is introduced only when adjusting the silicon-aluminum ratio; no artificially synthesized aluminum source is used, resulting in low carbon emissions. All four inexpensive zeolites can be rapidly and efficiently converted into SSZ-13 molecular sieves, exhibiting good activity and selectivity.

[0026] 2. The synthesis process can reduce the amount of expensive template agent N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH). The copper-tetraethylenepentamine (Cu-TEPA) complex not only acts as a template agent but also introduces copper into the molecular sieve framework during the reaction. Post-treatment only requires the removal of excess copper and sodium / potassium ions, eliminating copper ion exchange and other post-treatment steps, thus significantly reducing the generation of copper-containing wastewater. Simultaneously, rare earth metals are directly introduced during the reaction, eliminating the need for multiple exchange and calcination processes involving copper-containing and rare earth metal-containing solutions. Compared to using the copper-tetraethylenepentamine (Cu-TEPA) complex alone as a template agent, the use of a mixed template agent can improve the yield and relative crystallinity of the synthesized product, and enhance the activity and selectivity of the ammonia selective catalytic reduction reaction (NH3-SCR).

[0027] 3. The synthesis process begins by dispersing the copper-tetraethylenepentamine complex (Cu-TEPA) and rare earth metal compounds in deionized water. After thorough stirring, a silicon source, inexpensive zeolite, and seed crystals are added. Then, an alkali source and N,N,N-trimethyladamantyl ammonium hydroxide are added. This feeding method ensures that the silicon source and rare earth metals are well distributed in the solution, avoiding the decrease in yield and relative crystallinity caused by the formation of silica-alumina gel. It also ensures that the rare earth metals are uniformly distributed within the cages of the SSZ-13 molecular sieve. Furthermore, it facilitates the simultaneous binding of copper to two framework aluminum atoms in the six-membered ring and one framework aluminum atom in the eight-membered ring during the molecular sieve synthesis process, improving the low-temperature and high-temperature performance of the ammonia selective catalytic reduction reaction (NH3-SCR).

[0028] 4. This synthesis method significantly shortens the crystallization time compared to conventional synthesis of SSZ-13 molecular sieves, simplifies the operation steps, reduces production costs, and lowers carbon emissions, making it environmentally friendly. The obtained product has a high solid-phase yield.

[0029] The synthesized Cu / rare earth-SSZ-13 molecular sieve exhibits good crystal morphology and stable performance, with the silicon-aluminum ratio adjustable within a certain range.

[0030] 5. The use of rare earth metal ions can balance the charge of the molecular sieve framework, improve its stability, and prevent partial collapse of the framework caused by dealuminization under high-temperature hydrothermal conditions. It also prevents copper ions from detaching from the molecular sieve and freeing themselves on the framework surface to form copper oxide clusters (CuO). x This leads to a decrease in the activity and selectivity of the ammonia selective catalytic reduction reaction (NH3-SCR). Therefore, the hydrothermal stability of Cu-SSZ-13 molecular sieves modified with rare earth metal ions is significantly improved. Further research on the synthesis of SSZ-13 molecular sieves and their large-scale industrial application are of great significance.

[0031] Compared to the comparative examples provided in this invention, the molecular sieves prepared in the embodiments of this invention all achieved yields of over 80%, an improvement of 7% to 26%; the relative crystallinity all reached over 90%, an improvement of 2% to 21%; the reaction time was 8 to 20 hours, while the longest reaction time in the comparative examples was 30 hours. The molecular sieve fresheners prepared in the embodiments of this invention achieved 95% to 100% yields in the NH3-SCR reaction within a temperature range of 250℃ to 450℃, an improvement of 1% to 5% compared to the comparative examples provided in this invention. The molecular sieves prepared in the embodiments of this invention, after hydrothermal aging, achieved 85% to 100% yields in the NH3-SCR reaction within a temperature range of 250℃ to 450℃, an improvement of 5% to 25% compared to the comparative examples provided in this invention. Attached Figure Description

[0032] Figure 1 X-ray powder diffraction (XRD) patterns of Examples 1-7 and Comparative Examples 1-4.

[0033] Figure 2 : Scanning electron microscope (SEM) image of Example 5.

[0034] Figure 3 Evaluation diagram of ammonia selective catalytic reduction (NH3-SCR) of Cu / rare earth-SSZ-13 fresh agent prepared in Examples 1, 2, 3, 5 and 7.

[0035] Figure 4 Evaluation diagram of ammonia selective catalytic reduction (NH3-SCR) of Cu / rare earth-SSZ-13 fresh agent prepared in Example 5 and Comparative Examples 1, 2, 3 and 4.

[0036] Figure 5 Evaluation diagram of the selective catalytic reduction (NH3-SCR) of ammonia after hydrothermal aging of Cu / rare earth-SSZ-13 prepared in Examples 1, 2, 3, 5 and 7.

[0037] Figure 6 Evaluation diagram of the ammonia selective catalytic reduction reaction (NH3-SCR) of Cu / rare earth-SSZ-13 after hydrothermal aging prepared in Example 5 and Comparative Examples 1, 2, 3 and 4. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The specific embodiments described are only for explanation and illustration of the present invention and are not intended to limit the present invention.

[0039] Example 1:

[0040] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0041] Step 1: Mix copper sulfate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum nitrate and stir until homogeneous. Next, add sodalite (silicon-aluminum oxide molar ratio = 1.5:1), silica sol, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Then add potassium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), stirring until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.14, y = 0.96, z = 0.03, a = 0.27, and b = 55. The molar ratio of copper sulfate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 1% of the sum of the masses of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum nitrate is 1% of the sum of the masses of the inexpensive zeolite and the silicon source solid.

[0042] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 140℃, and the crystallization time is 20 hours.

[0043] Step 3: The crystallized product obtained in Step 2 was washed until pH=7, dried, and calcined to obtain molecular sieve powder. The drying temperature was 120℃, the drying time was 12h, and the calcination temperature was 550℃, the calcination time was 5h. The powder was then subjected to ammonia exchange with ammonium chloride. The solid-liquid ratio of the exchange was 1:20, the exchange temperature was 40℃, and the time was 2h. After the exchange was completed, the powder was dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0044] Example 2:

[0045] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0046] Step 1: Mix copper nitrate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum acetate and stir until homogeneous. Next, add analcime (silicon-aluminum oxide molar ratio = 4:1), silica, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Then add sodium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), stirring until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.10, y = 0.70, z = 0.02, a = 0.20, and b = 40. The molar ratio of copper nitrate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 3% of the sum of the mass of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum acetate is 5% of the sum of the mass of the inexpensive zeolite and the silicon source solid.

[0047] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 180℃, and the crystallization time is 14 hours.

[0048] Step 3: The crystallized product obtained in Step 2 was washed until pH=7, dried, and calcined to obtain the molecular sieve powder. The drying temperature was 120℃, the drying time was 12h, and the calcination temperature was 550℃, the calcination time was 5h. The powder was then subjected to ammonia exchange with ammonium nitrate. The solid-liquid ratio of the exchange was 1:20, the exchange temperature was 50℃, and the time was 2h. After the exchange was completed, the powder was dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0049] Example 3:

[0050] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0051] Step 1: Mix copper acetate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum chloride and stir until homogeneous. Next, add type X zeolite (silicon-aluminum oxide molar ratio = 2.5:1), silicon powder, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Then add potassium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), stirring until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.04, y = 0.28, z = 0.01, a = 0.08, and b = 15. The molar ratio of copper acetate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 5% of the sum of the mass of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum chloride is 10% of the sum of the mass of the inexpensive zeolite and the silicon source solid.

[0052] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 200℃, and the crystallization time is 8 hours.

[0053] Step 3: The crystallized product obtained in Step 2 is washed until pH=7, dried, and calcined to obtain molecular sieve powder. The drying temperature is 120℃, the drying time is 12h, and the calcination temperature is 550℃, the calcination time is 5h. The powder is then subjected to ammonia exchange with ammonium sulfate. The solid-liquid ratio of the exchange is 1:20, the exchange temperature is 60℃, and the time is 2h. After the exchange is completed, the powder is dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0054] Example 4:

[0055] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0056] Step 1: Mix copper sulfate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum nitrate and stir until homogeneous. Next, add type X zeolite (silicon-aluminum oxide molar ratio = 3:1), silica sol, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Then add sodium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), stirring until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.14, y = 0.96, z = 0.03, a = 0.27, and b = 55. The molar ratio of copper sulfate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 1% of the sum of the masses of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum nitrate is 1% of the sum of the masses of the inexpensive zeolite and the silicon source solid.

[0057] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 140℃, and the crystallization time is 20 hours.

[0058] Step 3: The crystallized product obtained in Step 2 is washed until pH=7, dried, and calcined to obtain molecular sieve powder. The drying temperature is 120℃, the drying time is 12h, and the calcination temperature is 550℃, the calcination time is 5h. The powder is then subjected to ammonia exchange with ammonium carbonate. The solid-liquid ratio of the exchange is 1:20, the exchange temperature is 70℃, and the time is 2h. After the exchange is completed, the powder is dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0059] Example 5:

[0060] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0061] Step 1: Mix copper nitrate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum acetate and stir until homogeneous. Next, add type A zeolite (silicon-aluminum oxide molar ratio = 2:1), silica, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Finally, add potassium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH) and stir until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.10, y = 0.70, z = 0.02, a = 0.20, and b = 40. The molar ratio of copper nitrate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 3% of the sum of the mass of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum acetate is 5% of the sum of the mass of the inexpensive zeolite and the silicon source solid.

[0062] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 180℃, and the crystallization time is 14 hours.

[0063] Step 3: The crystallized product obtained in Step 2 is washed until pH=7, dried, and calcined to obtain molecular sieve powder. The drying temperature is 120℃, the drying time is 12h, and the calcination temperature is 550℃, the calcination time is 5h. The powder undergoes ammonia exchange with ammonium bicarbonate. The solid-liquid ratio of the exchange is 1:20, the exchange temperature is 80℃, and the time is 2h. After the exchange is completed, it is dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0064] Example 6:

[0065] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application are described below.

[0066] Step 1: Mix copper acetate, deionized water, and tetraethylenepentamine (TEPA) thoroughly, then add lanthanum chloride and stir until homogeneous. Next, add type A zeolite (silicon-aluminum oxide molar ratio = 2.5:1), silicon powder, and SSZ-13 seed crystals sequentially, stirring until homogeneous. Then add sodium hydroxide and N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH) and stir until homogeneous to obtain the initial gel. The molar ratio of the substances used is xAl₂O₃:SiO₂:yM₂O:zR:aCu-TEPA:bH₂O, where x = 0.04, y = 0.28, z = 0.01, a = 0.08, and b = 15. The molar ratio of copper acetate to tetraethylenepentamine is 1:1. The mass of the seed crystals is 5% of the sum of the mass of the inexpensive zeolite and the silicon source solid, and the mass of lanthanum chloride is 10% of the sum of the mass of the inexpensive zeolite and the silicon source solid.

[0067] Step 2: Transfer the initial gel obtained in Step 1 to a stainless steel, polytetrafluoroethylene-lined high-pressure reactor for crystallization. The crystallization temperature is 200℃, and the crystallization time is 8 hours.

[0068] Step 3: The crystallized product obtained in Step 2 was washed until pH=7, dried, and calcined to obtain molecular sieve powder. The drying temperature was 120℃, the drying time was 12h, and the calcination temperature was 550℃, the calcination time was 5h. The powder was then subjected to ammonia exchange with ammonium chloride. The solid-liquid ratio of the exchange was 1:20, the exchange temperature was 90℃, and the time was 2h. After the exchange, the powder was dried at 120℃ for 12h and calcined at 550℃ for 5h to obtain Cu / La-SSZ-13 molecular sieve.

[0069] Example 7:

[0070] The preparation method and application of Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite are described. The three steps are the same as in Example 5, except that the rare earth metal used is replaced with cerium nitrate.

[0071] Comparative Example 1:

[0072] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite and its application is disclosed. The three steps are the same as in Example 5, except that aluminum sulfate is used as the aluminum source instead of type A zeolite, and the reaction time is 30 h.

[0073] Comparative Example 2:

[0074] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite and its application is disclosed. The three steps are the same as in Example 5, except that the amount of lanthanum acetate used is 0.

[0075] Comparative Example 3:

[0076] The preparation method and application of Cu / rare earth-SSZ-13 molecular sieve by one-step crystallization of inexpensive zeolite are described with reference to Example 5 mentioned in Chinese Patent CN201610552897.8.

[0077] Comparative Example 4:

[0078] A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite and its application are disclosed. The three steps are the same as in Example 5, except that the template agent used is a complex of copper and tetraethylenepentamine (Cu-TEPA). The molar ratio of each substance used is xAl2O3:SiO2:yM2O:zR:aCu-TEPA:bH2O, x=0.10,y=0.70,z=0,a=0.20,b=40, the crystallization temperature is 160℃, and the reaction time is 96h.

[0079] Table 1 shows the test results of the Cu / rare earth-SSZ-13 molecular sieves synthesized in Examples 1-7 and Comparative Examples 1-4:

[0080]

[0081]

[0082] Test characterization:

[0083] The detection instruments used in this invention are: X-ray powder diffractometer (model Panalytical X'Pert Powder, XRD), scanning electron microscope (model HITACHI S-3400N, SEM), and Fourier transform infrared analyzer (model MKSMultiGas 6030).

[0084] Activity evaluation of molecular sieves for ammonia selective catalytic reduction (NH3-SCR): Fresh and aged samples of the synthesized molecular sieves were evaluated for activity. Hydrothermal aging conditions were 800℃, 16h, and 10 vol% H2O. 0.1 g of fresh / aged sample and 1 g of quartz sand (both 40-60 mesh) were placed in a quartz tube reactor for activity evaluation. The SCR detection conditions used were 500 ppm NO, 500 ppm NH3, 5% O2, 8% CO2, 3.5% H2O, and a volume hourly space velocity (VHSV) of 40000 h⁻¹. -1 The selective catalytic reduction of ammonia was carried out at 100℃~600℃, and online measurement and quantitative analysis were performed using a Fourier transform infrared analyzer.

[0085] Examples 1-7 and Comparative Examples 1-4 were characterized using X-ray powder diffraction, and the results are shown in Table 1. The formulas for calculating the yield and relative crystallinity are as follows:

[0086]

[0087]

[0088] As shown in Table 1, the XRD patterns of Examples 1-7 and Comparative Examples 1-4 have peak positions that are essentially the same as the standard SSZ-13 (CHA structure) spectrum given by the International Zygote Association (IZA), proving that the four inexpensive zeolite transformation products are identical, all being SSZ-13 molecular sieves with a CHA structure. The peak positions of Examples 5, 7, and Comparative Example 2 are essentially the same, indicating that the presence of rare earth metals did not affect their crystal structure. Figure 2 It can be seen that the Cu / rare earth-SSZ-13 molecular sieve synthesized in Example 5 exhibits a cubic structure with a regular and complete morphology and a particle size of about 2 μm.

[0089] The silicon-to-aluminum ratio of the Cu / rare earth-SSZ-13 molecular sieves synthesized in Examples 1-7 was basically the same as that of the feed silicon-to-aluminum ratio, achieving control and adjustment of the silicon-to-aluminum ratio of the Cu / rare earth-SSZ-13 molecular sieves within a certain range. The yields of the Cu / rare earth-SSZ-13 molecular sieves synthesized in Examples 1-7 were high, all above 80%, and the relative crystallinity was all above 90%, indicating complete crystallization. Compared with Example 5, Comparative Example 1 had a longer reaction time and lower yield and relative crystallinity. Based on the XRD results, it was judged that Comparative Example 1 may have amorphous products, indicating that compared with the synthesis using amorphous raw materials, the crystallization method can synthesize products with higher yields and better relative crystallinity in a relatively shorter time. Compared with Example 5, Comparative Example 3 used a larger amount of N,N,N-trimethyladamantyl ammonium hydroxide (TMAdaOH), had a longer reaction time, and a lower yield. It is speculated that this is because the presence of silicon-aluminum gel caused some silicon-aluminum to dissolve in the mother liquor. Compared to Example 5, Comparative Example 4 had a longer reaction time and a significant decrease in both yield and relative crystallinity.

[0090] Depend on Figure 3 and Figure 4 It can be seen that the low-temperature conversion rate, high-temperature conversion rate, and maximum conversion rate of Examples 1, 2, 3, and 5 are basically the same, indicating that the performance of the four inexpensive zeolite transformation products is similar. The low-temperature conversion rate and maximum conversion rate of Examples 5 and 7 are basically the same, but the high-temperature conversion rate of Example 5 is higher than that of Example 7, indicating that compared with metallic cerium, metallic lanthanum is beneficial to improving the high-temperature performance of molecular sieves. The low-temperature conversion rate, high-temperature conversion rate, and maximum conversion rate of Comparative Example 1 are all lower than those of Example 5, indicating that compared with synthesis using amorphous synthesis as raw material, molecular sieves synthesized by the transformation method have good SCR effect. The low-temperature conversion rate and maximum conversion rate of Example 5 and Comparative Example 2 are basically the same, but the high-temperature conversion rates of Examples 5 and 7 are significantly better than those of Comparative Example 2, indicating that rare earth metals help improve the high-temperature performance of molecular sieves. The low-temperature conversion rate, maximum conversion rate, and high-temperature conversion rate of Comparative Example 3 are all lower than those of Example 5, presumably because the excessive copper content leads to the formation of copper oxide clusters (CuO). x The formation of [a specific type of zeolite] greatly affects its activity and selectivity. Comparative Example 4 showed lower conversion rates at low temperatures, maximum conversion rates, and high temperatures than Example 5, demonstrating that the Cu / rare earth-SSZ-13 zeolite synthesized with mixed template agents has a better SCR conversion rate compared to the zeolite synthesized with Cu-TEPA as a single template agent.

[0091] Depend on Figure 5 and Figure 6It can be seen that the low-temperature conversion rate, high-temperature conversion rate, and maximum conversion rate of Examples 1, 2, 3, and 5 are basically the same, indicating that the hydrothermal properties of the four inexpensive zeolite transformation products are similar. The low-temperature conversion rate, high-temperature conversion rate, and maximum conversion rate of Comparative Example 1 are all lower than those of Example 5, indicating that the molecular sieve synthesized by the transformation method has stronger hydrothermal activity compared to synthesis using amorphous synthesis as a raw material. The low-temperature conversion rate and maximum conversion rate of Examples 5 and 7 are similar to those of Comparative Example 2, while the high-temperature conversion rate of Examples 5 and 7 is significantly better than that of Comparative Example 2, indicating that rare earth metals can significantly improve the hydrothermal performance of Cu-SSZ-13 in the high-temperature range. The low-temperature conversion rate, maximum conversion rate, and high-temperature conversion rate of Comparative Example 3 are all lower than those of Example 5, presumably because the excessively high copper content leads to the formation of copper oxide clusters (CuO). x The formation of [a specific type of zeolite] greatly affects its activity and selectivity. Comparative Example 4 showed significantly lower conversion rates at low temperatures, maximum conversion rates, and high temperatures compared to Example 5, demonstrating that the Cu / rare earth-SSZ-13 molecular sieve synthesized with mixed template agents exhibits better SCR conversion rates than the molecular sieve synthesized with a single Cu-TEPA template agent.

[0092] Although the present invention has been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit of the present invention, and these modifications are all within the protection scope of the present invention.

Claims

1. A method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite, characterized in that, Includes the following steps: The complex of copper and tetraethylenepentamine and rare earth metal salts were dispersed in deionized water and stirred evenly. Inexpensive zeolite, silicon source and seed crystals were added in sequence and stirred evenly. Then, alkali source and N,N,N-trimethyladamantyl ammonium hydroxide were added and stirred evenly to obtain the initial gel. The initial gel was transferred to a high-pressure reactor lined with polytetrafluoroethylene for crystallization; the crystallized product was washed, dried, and calcined to obtain molecular sieve powder; the molecular sieve powder was then subjected to ammonium exchange with an ammonium source to obtain Cu-SSZ-13 molecular sieve modified with rare earth metal salt; the inexpensive zeolite is one or more of sodalite, analgesic, X-type zeolite, and A-type zeolite.

2. The preparation method of Cu / rare earth-SSZ-13 molecular sieve by one-step transformation of inexpensive zeolite according to claim 1, characterized in that, The initial molar ratio of the materials in the gel is: xAl2O3: SiO2: yM2O: zR: aCu-TEPA: bH2O, x=0.04~0.14, y=0.25~1, z=0.01~0.03, a=0.05~0.3, b=15~60; where M is the alkali metal ion in the alkali source, R is N,N,N-trimethyladamantylammonium hydroxide, Cu-TEPA is a copper-tetraethylenepentamine complex, and the molar ratio of copper ions to tetraethylenepentamine in the copper-tetraethylenepentamine complex is 1:

1. The mass of the seed crystal is 1%~5% of the sum of the mass of the inexpensive zeolite and the solid portion of the silicon source, and the mass of the rare earth metal salt is 1%~10% of the sum of the mass of the solid portion of the inexpensive zeolite and the silicon source.

3. The preparation method of Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite according to claim 1, characterized in that, The silicon source is one or more of silica sol, silica fume, and silicon powder.

4. The method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation of inexpensive zeolite according to claim 1, characterized in that, The alkali source is one or both of sodium hydroxide and potassium hydroxide; the seed crystal is SSZ-13 molecular sieve.

5. The method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation of inexpensive zeolite according to claim 1, characterized in that, The copper source in the copper-tetraethylenepentamine complex is one or more of copper sulfate, copper nitrate, or copper acetate.

6. The method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation crystallization of inexpensive zeolite according to claim 1, characterized in that, The rare earth metal salt contains one or both of lanthanum and cerium, and its source is one or more of the corresponding rare earth nitrates, rare earth acetates and rare earth chlorides.

7. The method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation of inexpensive zeolite according to claim 1, characterized in that, The crystallization temperature is 140~200℃, and the crystallization time is 8~20h.

8. The method for preparing Cu / rare earth-SSZ-13 molecular sieve by one-step transformation of inexpensive zeolite according to claim 1, characterized in that, The drying temperature is 120℃ and the drying time is 12h; the calcination temperature is 550℃ and the calcination time is 5h; the ammonium source in the ammonium exchange is one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, and ammonium bicarbonate, and the exchange temperature is 40℃~90℃.

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