SSZ-13 molecular sieve, method of making and use thereof

Abstract

The application belongs to the technical field of molecular sieve, and particularly relates to SSZ-13 molecular sieve and a preparation method and application thereof. The preparation method of the SSZ-13 molecular sieve comprises the following steps: mixing an alkali source and water, then adding an aluminum source, a template agent and a slow-release agent, stirring uniformly, controlling pH at 12-14, heating and ultrasonic dispersion, adding a silicon source to obtain initial slurry; first crystallizing the initial slurry at 80-100 DEG C, then increasing temperature to 125-180 DEG C for crystallization, filtering and washing with an ammonium salt solution, drying, calcining to obtain the SSZ-13 molecular sieve. The SSZ-13 molecular sieve is used for preparing a Cu-Bi-SSZ-13 catalyst. The SSZ-13 molecular sieve and the preparation method thereof are simple in process and low in cost, the molecular sieve has regular cubic small crystal grain morphology, and the application in the Cu-Bi-SSZ-13 catalyst solves the problem of sulfur poisoning.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve technology, specifically relating to SSZ-13 molecular sieve, its preparation method, and its application. Background Technology

[0002] SSZ-13 molecular sieve is a microporous molecular sieve with a chalcogenide (CHA) structure. Its framework consists of AlO4 and SiO4 tetrahedra connected by oxygen atoms in an orderly manner, forming ellipsoidal crystals with an eight-membered ring structure (pore size of approximately 0.38 nm). As a typical small-porous zeolite, SSZ-13 molecular sieve, with its large specific surface area, unique pore structure, and excellent thermal and hydrothermal stability, has shown broad application prospects in multiple catalytic fields, especially in selective catalytic reduction (SCR) denitrification of diesel vehicle exhaust, methanol-to-olefins (MTO), and hydrocracking reactions, attracting much attention.

[0003] In SCR denitrification applications, SSZ-13 molecular sieves are typically modified with copper (Cu) to prepare Cu-SSZ-13 catalysts. In these catalysts, copper ions serve as the main active centers, enabling highly efficient catalysis of the reaction between ammonia (NH3) and nitrogen oxides (NOx).

[0004] Currently, the preparation methods of SSZ-13 molecular sieves are mainly divided into conventional synthesis and one-step synthesis. Conventional synthesis typically requires introducing alkali metal cations such as sodium and potassium into the raw materials to balance the charge of the molecular sieve framework. First, M-SSZ-13 (M representing an alkali metal) molecular sieves are synthesized hydrothermally. Then, through a multi-step post-processing process, including high-temperature calcination to remove the template agent, ammonium ion exchange to remove the alkali metal, and copper salt solution ion exchange to introduce the active component, Cu-SSZ-13 catalyst is finally obtained. This method is lengthy and complex, energy-intensive, and time-consuming, and uses expensive template agents (such as N,N,N-trimethyl-1-adamantyl ammonium hydroxide), resulting in high production costs. More importantly, the large amount of waste liquid containing alkali metals and ammonium ions generated during the post-processing will cause water pollution and increase environmental treatment costs. Furthermore, CN110104658A points out that even after ion exchange, residual alkali metals can still catalyze the dealuminization of the molecular sieve framework and cause copper ion aggregation and deactivation under high-temperature hydrothermal conditions, severely affecting the hydrothermal stability of the catalyst.

[0005] To simplify the process and reduce costs, a one-step synthesis method (or in-situ synthesis method) directly adds a copper source to the initial gel, and Cu-SSZ-13 molecular sieves can be obtained through a single hydrothermal crystallization, eliminating the need for subsequent ion exchange steps. As disclosed in patent CN110104658A, although the process is shortened, it still introduces alkali metals. The presence of alkali metals results in a low silica-alumina ratio and high alkali metal content in the synthesized M / Cu-SSZ-13 molecular sieve, necessitating subsequent post-treatment with acid washing or ammonium salt exchange to remove the alkali metals. However, such post-treatment is not only ineffective in removing alkali metals, but the acid washing process also easily damages the molecular sieve's framework structure, generating silanol defects, thereby significantly reducing the catalyst's catalytic activity and hydrothermal stability.

[0006] To obtain SSZ-13 molecular sieves with regular morphology (e.g., cubic), small and uniformly distributed grain size, various strategies have been explored in existing technologies. For example, CN110156046A discloses a method for obtaining nanoscale SSZ-13 molecules by adding polyacrylamide as an additive to the synthesis system to inhibit grain growth. However, the molecular sieves synthesized by this method are in the hydrogen or sodium form, and still require a complex subsequent ion exchange process to convert them into active Cu-SSZ-13 catalysts. The process for directly synthesizing small-grained, regularly morphologically regular Cu-SSZ-13 molecular sieves that are free of alkali metals still faces significant challenges. Existing methods struggle to simultaneously achieve precise control over grain size (especially nanoscale cubic morphology), copper content, and silicon-to-aluminum ratio, often resulting in products with twinned or irregular morphologies and poor hydrothermal stability.

[0007] In practical applications, especially in complex exhaust gas treatment scenarios such as diesel vehicle exhaust, Cu-SSZ-13 catalysts face a severe challenge: sulfur poisoning. Sulfur dioxide (SO2) in the exhaust gas reacts with active copper species or the molecular sieve framework on the catalyst surface, generating stable sulfate or sulfite species, thus irreversibly poisoning the catalytic active sites. This sulfur poisoning phenomenon is particularly prominent at low temperatures (e.g., 200-300℃), severely inhibiting the catalyst's denitrification activity and nitrogen selectivity, leading to a sharp decline in its overall catalytic performance. For example, patent CN118929690A explicitly points out that sulfur dioxide significantly reduces the low-temperature activity of Cu-SSZ-13. To address this problem, a complex modification scheme is proposed. First, alkali metal-containing Cu-SSZ-13 is synthesized via steam-assisted crystallization. Then, the crystals are calcined twice, during which aluminum doping is performed using ion implantation. Finally, cerium modification is performed via liquid-phase reflux, causing CeO2 nanocrystals to coat the molecular sieve surface. Although this method improves the sulfur resistance of the catalyst to some extent, its preparation process involves high-temperature calcination, ion implantation and multi-step wet chemical treatment, which is extremely complex, requires high-end equipment and consumes a lot of energy. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide an SSZ-13 molecular sieve and its preparation method. The process is simple and low-cost, and it can directly synthesize alkali metal-free molecular sieves with regular cubic small crystal morphology. It can be used in Cu-Bi-SSZ-13 catalysts to solve the problem of sulfur poisoning.

[0009] The preparation method of the SSZ-13 molecular sieve of the present invention includes the following steps: a. Preparation of mixed slurry: Mix the alkali source and water, then add the aluminum source, template agent and slow-release agent, stir evenly, control the pH at 12~14, heat to 50~80℃ and ultrasonically disperse, add the silicon source to obtain the initial slurry; b. Segmented crystallization: The initial slurry is first crystallized at 80~100℃ for 6~12h, and then the temperature is raised to 125~180℃ for 6h~24h. c. Post-processing: The crystallized product was filtered and washed with ammonium salt solution, dried and calcined to obtain hydrogen-form SSZ-13 molecular sieve.

[0010] In step a, the alkali source is NaOH, the aluminum source is aluminum hydroxide or boehmite, and the template agent is a mixture of N,N,N-trimethyl-1-adamantyl ammonium hydroxide (SDA1) and tetramethylammonium hydroxide (SDA2) solutions. The molar ratio of SDA1 to SDA2 is 1:0.5~1.0.

[0011] The silicon source is tetraethyl orthosilicate or alkaline silica sol, and the slow-release agent is hexamethylenetetramine or a mixture of hexamethylenetetramine and urea.

[0012] The molar ratio of silicon source to aluminum source is 1:0.02~0.1; the molar ratio of silicon source to template agent is 1:0.075~0.1; and the molar ratio of silicon source to slow-release agent is 1:0.05~0.15.

[0013] In step a, heat to 50-80℃ and ultrasonically disperse for 30-60 minutes.

[0014] Step c, filtration and washing, uses a positive pressure filter. The ammonium salt solution is one of ammonium nitrate solution, ammonium chloride solution, or ammonium sulfate solution, with a concentration of 0.1~0.5 mol / L.

[0015] Step c involves drying at 80-120℃ for 4-12 hours; calcination at 550-800℃ for 4-10 hours.

[0016] The SSZ-13 molecular sieve has cubic crystals with a size of 135~645nm.

[0017] The application of the SSZ-13 molecular sieve is as follows: SSZ-13 molecular sieve is mixed with Cu(NO3)2 and Bi(NO3)3, a binder is added, the mixture is slurried, and then coated onto a support using vacuum adsorption. The mixture is then dried and calcined to obtain a Cu-Bi-SSZ-13 catalyst. The binder is an aluminum sol, and the amount of binder added is 5% to 10% of the total mass of the SSZ-13 molecular sieve, Cu(NO3)2, and Bi(NO3)3.

[0018] The Cu-Bi-SSZ-13 catalyst, based on SSZ-13 molecular sieve, has a CuO loading of 2-5% and a Bi2O3 loading of 0.1-0.5%.

[0019] The coating is applied to a cordierite carrier using vacuum adsorption, then dried at 100-120℃ and calcined at 550-600℃ for 4-6 hours.

[0020] Specifically, the preparation method of SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix NaOH and water, then add aluminum hydroxide or boehmite, stir for 30-40 min, add SDA1 and SDA2, stir evenly, add hexamethylenetetramine or a mixture of hexamethylenetetramine and urea, mix and stir for 30-40 min, control the pH at 12-14, slowly add tetraethyl orthosilicate or alkaline silica sol, mix evenly, heat to 50-80℃ and ultrasonically disperse for 30-60 min to obtain the initial slurry; b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 80~100℃ for 6~12h, and then the temperature is raised to 125~180℃ for 6h~24h. c. Post-processing: The crystallized product is filtered and washed with 0.1~0.5mol / L ammonium salt solution (ammonium nitrate solution, ammonium chloride solution, ammonium sulfate solution) using a positive pressure filter, dried at 80~120℃ for 4~12h, and then calcined at 550~800℃ for 4~10h to obtain SSZ-13 molecular sieve.

[0021] This invention shortens the synthesis time by adding hexamethylenetetramine as a slow-release agent to replace part of the template agent and employing ultrasonic preheating and segmented crystallization. The added slow-release agent acts as a complexing agent, controlling the nucleation rate and inhibiting crystal size. The molecular sieve synthesized by this method has a small cubic morphology and a crystal size of 135~645nm.

[0022] This invention employs ultrasonic heat treatment at 50-80℃ during the pulping stage, and requires the pulp to be synthesized into a sol-like state during the gelation stage. The heat treatment is primarily used to ensure the slow-release alkali source is mixed evenly with the raw materials to prepare the initial gel. A traditional hydrothermal method is used for segmented crystallization: the first stage crystallization temperature is 80-100℃ for 6-12 hours, and the second stage crystallization temperature is 125-180℃ for 6-24 hours.

[0023] In this invention, ammonium salt solution is used for filtration and washing. The small-crystal SSZ-13 molecular sieve powder is exchanged with ammonium salt solution multiple times, then dried and calcined at 550°C to obtain hydrogen-form SSZ-13 molecular sieve.

[0024] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention provides a simple and low-cost method for preparing SSZ-13 molecular sieves. By adding hexamethylenetetramine or a mixture thereof as a slow-release agent, some expensive template agents are replaced. Combined with a segmented crystallization process, the synthesis cycle is significantly shortened, and production costs and energy consumption are greatly reduced. At the same time, ultrasonic heat treatment is used in the pulping stage to avoid raw material agglomeration, achieving the goal of directly synthesizing the target product without adding seed crystals, thus simplifying the process.

[0025] (2) This invention directly synthesizes cubic hydrogen-form SSZ-13 molecular sieves that are free of alkali metals, have a grain size of less than 645 nm, and exhibit regular morphology. Direct filtration and washing with ammonium salt solution effectively removes sodium ions introduced into the synthesis system, avoiding the problems of framework dealuminization and copper ion agglomeration caused by alkali metal residues in traditional methods. The resulting small-grained molecular sieve exhibits excellent resistance to hydrothermal aging, with a specific surface area decay rate of less than 5% after hydrothermal aging, significantly superior to SSZ-13 molecular sieves prepared by existing technologies.

[0026] (3) The Cu-Bi-SSZ-13 catalyst prepared by further loading copper and bismuth onto small-crystal SSZ-13 molecular sieves in this invention exhibits excellent catalytic performance in the NH3-SCR denitrification reaction, with NO catalytic activity in a wide temperature range of 200~600℃. x The conversion rate remained above 90%. Simultaneously, due to the synergistic effect of the bismuth component, the catalyst exhibited a conversion efficiency of over 80% even at low temperatures (below 150℃), and significantly improved resistance to sulfur dioxide (SO2) poisoning, effectively solving the technical problem of easy deactivation of existing Cu-SSZ-13 catalysts in sulfur-containing waste gas. Furthermore, after hydrothermal aging, NO... x The conversion rate remains above 80%, and the catalyst can maintain a conversion efficiency of over 70% even at low temperatures (before 150℃). Attached Figure Description

[0027] Figure 1 The XRD patterns are of molecular sieve samples 1# to 11# prepared in Examples 1 to 5 and Comparative Examples 1 to 6.

[0028] Figure 2 The image shown is a SEM image of sample 1# synthesized in Example 1.

[0029] Figure 3 The image shows the SEM image of sample 2# synthesized in Example 2.

[0030] Figure 4 The image shown is a SEM image of sample 3# synthesized in Example 3.

[0031] Figure 5 The image shown is a SEM image of sample 4# synthesized in Example 4.

[0032] Figure 6 This is a SEM image of sample 5# synthesized in Example 5.

[0033] Figure 7 The image shows the SEM image of sample 6# synthesized in Comparative Example 1.

[0034] Figure 8 The image shows the SEM image of sample 7# synthesized in Comparative Example 2.

[0035] Figure 9 The image shows the SEM image of sample 8# synthesized in Comparative Example 3.

[0036] Figure 10 The image shows the SEM image of sample 9# synthesized in Comparative Example 4.

[0037] Figure 11 This is a SEM image of sample 10# synthesized in Comparative Example 5.

[0038] Figure 12 The image shows the SEM image of sample 11# synthesized in Comparative Example 6. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments.

[0040] The template agent N,N,N-trimethyl-1-adamantyl ammonium hydroxide (SDA1) was a 25% mass concentration solution purchased directly; the tetramethyl ammonium hydroxide (SDA2) was a 25% mass concentration solution purchased directly.

[0041] Alkaline silica sol: SiO2 mass concentration is 30%.

[0042] The seed crystals used in Comparative Examples 1 and 2 were SSZ-13 molecular sieves purchased from Hunan Tianyi New Materials Co., Ltd., with a silicon-to-aluminum ratio (molar ratio): 22; Na₂O (wt%): <0.05; and BET specific surface area (m²). 2 / g): 530; Crystal size (typical): 1μm.

[0043] Example 1 The preparation method of the SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 17g SDA2 and stir evenly. Add 12.6g hexamethylenetetramine and mix and stir for 30min. The pH is 12~14. Mix evenly and heat to 50℃ for ultrasonic dispersion for 60min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.2 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 8 h, and then calcined at 550℃ for 6 h to obtain SSZ-13 molecular sieve, named Sample 1#. The SEM image of the sample is shown below. Figure 2 As shown, the edge length of the crystals is between 512.6 nm and 640.2 nm, with most concentrated around 600 nm, which belongs to the submicron molecular sieve.

[0044] Example 2 The preparation method of the SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 40min. Add 25g SDA1 and 17g SDA2 and stir evenly. Add 4.28g hexamethylenetetramine and mix and stir for 40min. The pH is 12~14. Mix evenly and heat to 80℃. Disperse ultrasonically for 30min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 180℃ for 6 hours. c. Post-processing: The crystallized product was filtered and washed with 0.5 mol / L ammonium chloride solution using a positive pressure filter, dried at 80℃ for 12 h, and then calcined at 800℃ for 4 h to obtain SSZ-13 molecular sieve, named Sample 2#. The SEM image of the sample is shown below. Figure 3As shown, the grain edge length is between 359.1nm and 551.2nm, with most concentrated in the 400-550nm range.

[0045] Example 3 The preparation method of the SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 17g SDA2 and stir evenly. Add 8.8g hexamethylenetetramine and 2.3g urea and mix and stir for 30min. The pH should be 12~14. Mix evenly and heat to 50℃. Disperse ultrasonically for 60min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 20 hours. c. Post-processing: The crystallized product was filtered and washed with 0.1 mol / L ammonium sulfate solution using a positive pressure filter, dried at 80℃ for 6 h, and then calcined at 550℃ for 10 h to obtain SSZ-13 molecular sieve, named Sample 3#. The SEM image of the sample is shown below. Figure 4 As shown, the grain edge length is between 375.4nm and 498.6nm, with most concentrated in the 370-500nm range.

[0046] Example 4 The preparation method of the SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 8.8g hexamethylenetetramine and 1.2g urea and mix and stir for 30min. The pH should be 12~14. Mix evenly and heat to 80℃. Disperse ultrasonically for 30min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 80°C for 12 hours, then the temperature is raised to 160°C for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.3 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 6 h, and then calcined at 600℃ for 6 h to obtain SSZ-13 molecular sieve, named Sample 4#. The SEM image of the sample is shown below. Figure 5 As shown, the grain edge length is between 135.1nm and 267.2nm, with most concentrated in the 180-250nm range.

[0047] Example 5 The preparation method of the SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then add 3.6g boehmite and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 12.6g hexamethylenetetramine and 1.2g urea and mix and stir for 30min. The pH should be 12-14. Mix evenly and heat to 50℃. Disperse ultrasonically for 60min. Slowly add 312g tetraethyl orthosilicate to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 125℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.3 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 6 h, and then calcined at 600℃ for 6 h to obtain SSZ-13 molecular sieve, named sample 5#. The SEM image of the sample is shown below. Figure 6 As shown, the grain edge length is between 149.0 nm and 251.2 nm, with most concentrated in the 170-250 nm range.

[0048] Example 6 Application of the SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 1 was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, and the mixture was slurried. The mixture was then coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 100°C and then calcined at 550°C for 4 hours to obtain a Cu-Bi-SSZ-13 catalyst. Based on the SSZ-13 molecular sieve, the CuO loading was 5% and the Bi2O3 loading was 0.1%.

[0049] Example 7 Application of the SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 2 was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, and the mixture was slurried. The mixture was then coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 100°C and then calcined at 550°C for 4 hours to obtain a Cu-Bi-SSZ-13 catalyst. Based on the SSZ-13 molecular sieve, the CuO loading was 2% and the Bi2O3 loading was 0.1%.

[0050] Example 8 Application of the SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 3 was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, and the mixture was slurried. The mixture was then coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 120°C and then calcined at 580°C for 5 hours to obtain a Cu-Bi-SSZ-13 catalyst. Based on the SSZ-13 molecular sieve, the CuO loading was 5% and the Bi2O3 loading was 0.1%.

[0051] Example 9 Application of the SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 4 was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, and the mixture was slurried. The mixture was then coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 100°C and then calcined at 600°C for 6 hours to obtain a Cu-Bi-SSZ-13 catalyst. Based on the SSZ-13 molecular sieve, the CuO loading was 2.5% and the Bi2O3 loading was 0.35%.

[0052] Example 10 Application of the SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 5 was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, the mixture was slurried, and coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 115℃ and then calcined at 550℃ for 5 hours to obtain a Cu-Bi-SSZ-13 catalyst. Based on the SSZ-13 molecular sieve, the CuO loading was 2% and the Bi2O3 loading was 0.5%.

[0053] Comparative Example 1 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 11g SDA2 and mix and stir for 30min. The pH should be between 12 and 14. Mix evenly and heat to 50℃ for ultrasonic dispersion for 60min. Slowly add 120g alkaline silica sol and 1.8g seed crystals to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.2 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 8 hours, and then calcined at 550℃ for 6 hours to obtain SSZ-13 molecular sieve, named sample 6#. The SEM image of the sample is shown below. Figure 7As shown, the grain edge length is between 817.8 nm and 1.311 μm, with most concentrated in the range of 1.0 to 1.2 μm. It belongs to the micron-scale molecular sieve and its size is significantly larger than that of the sample in the example.

[0054] Comparative Example 2 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 50g SDA1 and mix for 30min. The pH should be between 12 and 14. After mixing evenly, heat to 50℃ and ultrasonically disperse for 60min. Slowly add 120g alkaline silica sol and 1.8g seed crystals to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.2 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 8 hours, and then calcined at 550℃ for 6 hours to obtain SSZ-13 molecular sieve, named sample 7#. The SEM image of the sample is shown below. Figure 8 As shown, the grain edge length is between 1.650μm and 3.384μm, with most concentrated in the range of 2.0 to 3.0μm, which belongs to the large-size micron-scale molecular sieve.

[0055] Comparative Example 3 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 12g urea and stir for 30min. The pH should be 12~14. Mix evenly and heat to 80℃. Disperse ultrasonically for 30min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 80°C for 12 hours, then the temperature is raised to 160°C for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.3 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 6 h, and then calcined at 600℃ for 6 h to obtain SSZ-13 molecular sieve, named sample 8#. The SEM image of the sample is shown below. Figure 9 As shown, the grain edge length is between 821.8 nm and 1.076 μm, with most concentrated in the 800-1100 nm range. It belongs to the submicron molecular sieve, and its size is between the nanoscale and large micron scale samples.

[0056] Comparative Example 4 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 8.8g hexamethylenetetramine and mix and stir for 30min. The pH is 12~14. Mix evenly and heat to 50℃ for ultrasonic dispersion for 60min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 160°C for 30 hours. c. Post-processing: The crystallized product was filtered and washed with 0.2 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 8 hours, and then calcined at 550℃ for 6 hours to obtain SSZ-13 molecular sieve, named sample 9#. The SEM image of the sample is shown below. Figure 10 As shown, the particle size ranges from 35.07 nm to 101.2 nm, with most concentrated in the 40-80 nm range, which are typical nanoscale particles.

[0057] Comparative Example 5 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 8.8g hexamethylenetetramine and mix for 30min. The pH is 12~14. Mix evenly using conventional mechanical methods for 60min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with 0.2 mol / L ammonium nitrate solution using a positive pressure filter, dried at 100℃ for 8 hours, and then calcined at 550℃ for 6 hours to obtain SSZ-13 molecular sieve, named sample 10#. The SEM image of the sample is shown below. Figure 11 As shown, the edge length of a single crystallite is between 130.6 nm and 193.6 nm, which is typical of nanoscale molecular sieve crystallites.

[0058] Comparative Example 6 A method for preparing SSZ-13 molecular sieve includes the following steps: a. Preparation of mixed slurry: Mix 5.3g NaOH and 15g water, then slowly add 3.7g aluminum hydroxide and stir for 30min. Add 25g SDA1 and 8.5g SDA2 and stir evenly. Add 8.8g hexamethylenetetramine and mix and stir for 30min. The pH is 12~14. Mix evenly and heat to 50℃ for ultrasonic dispersion for 60min. Slowly add 120g alkaline silica sol to obtain the initial slurry. b. Segmented crystallization: The initial slurry is transferred to a high-pressure reactor and crystallized at 100℃ for 6 hours, then the temperature is raised to 160℃ for 24 hours. c. Post-processing: The crystallized product was filtered and washed with deionized water using a positive pressure filter, dried at 100℃ for 8 hours, and then calcined at 550℃ for 6 hours to obtain SSZ-13 molecular sieve, named Sample 11#. The SEM image of the sample is shown below. Figure 12 As shown, the grain edge length is between 193.7 nm and 285.1 nm, with most concentrated in the 200-280 nm range, which belongs to the nanoscale molecular sieve.

[0059] Comparative Example 7 An application of SSZ-13 molecular sieve: The SSZ-13 molecular sieve prepared in Example 1 was mixed with Cu(NO3)2, a binder was added, the mixture was slurried, and coated onto a cordierite support by vacuum adsorption. The mixture was first dried at 110°C and then calcined at 550°C for 4 h to obtain a Cu-SSZ-13 catalyst with a CuO loading of 5% based on the SSZ-13 molecular sieve.

[0060] Comparative Examples 8 to 13 The molecular sieve samples prepared in Comparative Examples 1 to 6 were all processed using the same procedure as in Example 6 to prepare the corresponding catalysts.

[0061] (1) XRD patterns of molecular sieve samples 1#~11# prepared in Examples 1 to 5 and Comparative Examples 1 to 6, as shown in the figure. Figure 1 As shown in the figure, the target molecular sieves were prepared in Examples 1 to 5 and Comparative Examples 1 to 6. The peaks of 1# to 5# are sharp, with low and smooth baselines, indicating that the molecular sieves have high crystallinity, complete crystal development, and no obvious amorphous impurities. The peak intensities of some samples (such as 3# to 5# and 7# to 9#) of 6# to 11# are slightly reduced, and the baselines are slightly raised, indicating that the crystallinity has decreased to varying degrees.

[0062] (2) The molecular sieves prepared in Examples 1 to 5 and Comparative Examples 1 to 6 were tested, and the test results are shown in Table 1.

[0063] Hydrothermal aging test specific surface area aging decay rate: The samples were subjected to hydrothermal aging under the same conditions: 800℃, 24h, water vapor content 10%, and water vapor mixed with air flow rate of 500mL / min. (Decay rate = (initial specific surface area - aged specific surface area) / initial specific surface area).

[0064] Table 1 Test Results

[0065] As shown in Table 1, the hydrothermal aging degradation rates of samples 1-5# are all lower than those of the comparative sample 6#, remaining at around 5%. In contrast, the degradation rates of molecular sieves synthesized using traditional methods range from 10.45% to 15.38%, indicating that the samples synthesized in this invention all possess excellent hydrothermal stability.

[0066] (3) Application evaluation: The catalysts of Examples 6 to 10, and Comparative Examples 7, 8 to 13, were subjected to NH3-SCR activity determination according to the following steps: 0.5g of catalyst sample particles were placed in a reaction tube, which was then placed in an electric furnace. Gas was introduced through the connected pipeline, and the airtightness of the apparatus was checked. The reaction gas was then converted to a reaction gas with the following composition: NO: 500ppm, NH3: 500ppm, O2: 5%, SO2: 300ppm, and the remainder being N2 equilibrium gas. The total gas flow rate was 750mL / min. The initial temperature was stabilized for 120min, and the remaining temperature was stabilized for 30min before activity evaluation. The temperature range was 150~600℃. The results are shown in Table 2. Table 2 shows that Examples 6~10 (Cu-Bi-SSZ-13) exhibited excellent denitrification activity across the entire temperature range of 150~600℃, with a conversion rate exceeding 80% at a low temperature of 150℃. The NO concentration was significantly higher in the 200~600℃ range. x The conversion rate remained stable above 92%, with an extremely wide conversion window. Comparative Example 7 (Bi-free Cu-SSZ-13) showed significantly lower activity, only 33% at 150℃, and a rapid decline at higher temperatures (>500℃). Comparative Examples 8-13 (catalysts prepared using other molecular sieves) showed some improvement over Comparative Example 7, but their low-temperature activity (150℃) was generally only around 50%, and their high-temperature activity (>500℃) also showed significant decline, resulting in overall performance significantly inferior to the examples.

[0067] The catalyst samples from Examples 6 to 10, and Comparative Examples 7, 8 to 13, were evaluated after thermal aging, following the same evaluation process as described above. The results are shown in Table 3. Table 3 shows that Examples 6 to 10 maintained excellent activity after aging: conversion rate ≥75% at 150℃, and mostly above 80% in the 200-600℃ range, indicating excellent resistance to hydrothermal aging. Comparative Example 7 showed severe activity degradation after aging, with only 20% at 150℃ and decreasing to 20-40% at higher temperatures. Comparative Examples 8 to 13 generally showed low-temperature activity below 55% after aging, and mostly below 50% at high temperatures (>500℃), indicating significantly inferior anti-aging performance compared to the examples.

[0068] Table 2. NH3-SCR Activity Evaluation Results of Catalyst Samples

[0069] Table 3. NH3-SCR Activity Evaluation Results of Catalyst Samples After Hydrothermal Aging

Claims

1. A method for preparing SSZ-13 molecular sieve, characterized in that, Includes the following steps: a. Preparation of the mixed slurry: Mix the alkali source and water, then add the aluminum source, template agent, and slow-release agent, stir evenly, control the pH at 12-14, heat to 50-80℃ and ultrasonically disperse, add the silicon source to obtain the initial slurry; in step a, the alkali source is NaOH, the aluminum source is aluminum hydroxide or boehmite, the template agent is a mixed template agent of N,N,N-trimethyl-1-adamantyl ammonium hydroxide and tetramethyl ammonium hydroxide solution, the silicon source is tetraethyl orthosilicate or alkaline silica sol, and the slow-release agent is hexamethylenetetramine or a mixture of hexamethylenetetramine and urea; the molar ratio of silicon source to aluminum source is 1:0.02-0.1; the molar ratio of silicon source to template agent is 1:0.075-0.1; the molar ratio of silicon source to slow-release agent is 1:0.05-0.15; b. Segmented crystallization: The initial slurry is first crystallized at 80~100℃ for 6~12h, and then the temperature is raised to 125~180℃ for 6h~24h. c. Post-processing: The crystallized product was filtered and washed with ammonium salt solution, dried and calcined to obtain SSZ-13 molecular sieve.

2. The method for preparing SSZ-13 molecular sieve according to claim 1, characterized in that, In step a, heat to 50-80℃ and ultrasonically disperse for 30-60 minutes.

3. The method for preparing SSZ-13 molecular sieve according to claim 1, characterized in that, Step c, filtration and washing, uses a positive pressure filter. The ammonium salt solution is one of ammonium nitrate, ammonium chloride, or ammonium sulfate, with a concentration of 0.1~0.5 mol / L.

4. The method for preparing SSZ-13 molecular sieve according to claim 3, characterized in that, Step c involves drying at 80-120℃ for 4-12 hours; calcination at 550-800℃ for 4-10 hours.

5. An SSZ-13 molecular sieve, characterized in that, It is prepared by the method of SSZ-13 molecular sieve according to any one of claims 1 to 4, wherein the crystals of the SSZ-13 molecular sieve are cubic with a size within 135 nm to 645 nm.

6. An application of the SSZ-13 molecular sieve according to claim 5, characterized in that, SSZ-13 molecular sieve was mixed with Cu(NO3)2 and Bi(NO3)3, a binder was added, the mixture was slurried and coated onto a support by vacuum adsorption, dried and then calcined to obtain Cu-Bi-SSZ-13 catalyst.

7. The application of the SSZ-13 molecular sieve according to claim 6, characterized in that, The Cu-Bi-SSZ-13 catalyst, based on SSZ-13 molecular sieve, has a CuO loading of 2-5% and a Bi2O3 loading of 0.1-0.5%.

8. The application of the SSZ-13 molecular sieve according to claim 6, characterized in that, The coating is applied to a cordierite carrier using vacuum adsorption, then dried at 100-120℃ and calcined at 550-600℃ for 4-6 hours.

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