Method for synthesizing SAPO-34 molecular sieve using catalytic cracking catalyst residue

Abstract

A method for synthesizing SAPO-34 molecular sieve using catalytic cracking catalyst residue includes the following steps: (1) the modified molecular sieve residue is activated by high-temperature steam; (2) inorganic acid is added to the activated residue for secondary hydrothermal activation; (3) aluminum source, phosphorus source and template agent are added to the residue solution after secondary activation to prepare a mixed solution; (4) the mixed solution is aged at room temperature and then heated for hydrothermal crystallization to obtain a crystallized solution; (5) the crystallized solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve. The SAPO molecular sieve prepared by this invention has high crystallinity and can realize the reuse of silicon and aluminum resources in catalyst plants.

Description

Technical Field

[0001] This invention relates to a method for synthesizing SAPO-34 molecular sieve using rubber residue. Background Technology

[0002] The production of catalytic cracking catalysts includes steps such as the synthesis and modification of Y-type molecular sieves, gelation of modified Y-type molecular sieves with matrix components, spray drying, washing, and calcination. Wastewater is generated during the synthesis, modification, and washing of molecular sieves, as well as during the gelation and washing of the catalyst. After sedimentation, filtration, and slag removal, the wastewater yields a residue mainly composed of Al₂O₃ and SiO₂, known as gel residue. Directly discarding this residue wastes resources such as Si and Al. Utilizing it using industrially feasible and cost-effective technologies can not only alleviate the environmental burden on enterprises but also reduce production costs and improve economic efficiency. However, the silicon and aluminum in this gel residue differ from commonly used silicon and aluminum raw materials, making direct utilization difficult to achieve satisfactory results.

[0003] SAPO-34 molecular sieve has a typical CHA topology, and its framework is mainly composed of PO 2+ AlO 2- SiO2 tetrahedra are interconnected, and these framework atoms are periodically arranged into six-membered, four-membered, and eight-membered rings, ultimately forming an ellipsoidal CHA cage structure and a three-dimensional intersecting channel structure. SAPO-34 is actually formed by Si atoms replacing AlPO4 framework atoms, because in the AlPO4 framework, PO... 2+ and AlO 2- The tetrahedra carry both positive and negative charges in equal numbers, resulting in an electrically neutral framework with weak surface acidity. However, introducing Si atoms into the framework disrupts this charge balance, causing the molecular sieve to become negatively charged overall. SAPO-34 also contains both Lewis acid and Beta acid centers on its surface. Therefore, SAPO-34 exhibits excellent hydrothermal stability, suitable surface acidity, and a well-defined pore structure.

[0004] Currently, there are four main methods for synthesizing SAPO-34: hydrothermal synthesis, vapor-phase crystallization, microwave synthesis, and ultrasonic synthesis. Hydrothermal synthesis is the most widely used and mature method, with its main raw materials including silicon, aluminum, phosphorus, template agents, and deionized water. Commonly used silicon sources include silica sol, activated SiO2, and orthosilicates; aluminum sources include activated alumina, boehmite, and aluminum isopropoxide; template agents can include tetraethylammonium hydroxide (TEAOH), triethylamine, diethylamine, and morpholine; and phosphoric acid is generally used as the phosphorus source. However, these raw materials are all expensive chemical reagents, resulting in a high cost for SAPO-34 synthesis. The abundant silicon and aluminum sources in slag are relatively inexpensive. Utilizing the silicon and aluminum sources in slag to synthesize SAPO-34 would be significant for green emission reduction in catalyst plants and lowering the cost of molecular sieve synthesis. However, slag cannot be directly used to synthesize SAPO-34 molecular sieves; currently, there is no method for synthesizing SAPO-34 molecular sieves with high crystallinity using slag. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for synthesizing SAPO-34 molecular sieves using waste silicon and aluminum from catalytic cracking catalyst residue.

[0006] This invention provides a method for using SAPO-34 molecular sieves (referred to as catalytic cracking catalyst slag, or simply slag) produced by catalytic cracking catalysts, comprising the following steps:

[0007] (1) The catalytic cracking catalyst slag is activated by high temperature steam to obtain the slag after one activation.

[0008] (2) Add inorganic acid and water to the glue residue after the first activation and perform a second hydrothermal activation to obtain a glue residue slurry after the second activation.

[0009] (3) After secondary activation, aluminum source, optional silicon source, phosphorus source and template agent are added to the glue residue slurry to prepare a mixed solution;

[0010] (4) After the mixed solution is aged by stirring at room temperature, it is heated to carry out hydrothermal crystallization to obtain a crystallized solution;

[0011] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0012] The rubber residue used can be waste rubber residue obtained from wastewater generated in the production of catalytic cracking catalysts through sedimentation, filtration and slag cutting.

[0013] According to the present invention, based on the dry weight of the resin residue, the resin residue contains 0-9% by weight of Na2O, 20-60% by weight of Al2O3, 20-60% by weight of SiO2, and 0-15% by weight of RE2O3.

[0014] In one embodiment, the catalytic cracking catalyst residue is a residue produced by molecular sieve modification. The molecular sieve modification typically includes treating the molecular sieve with steam and / or with fumed silicon tetrachloride, washing, and optionally exchanging the molecular sieve. The molecular sieve modified is, for example, a Y-type molecular sieve.

[0015] In one embodiment, the slag produced by the molecular sieve modification is the slag produced by the modification of Y-type molecular sieves.

[0016] Preferably, the gel residue produced by the molecular sieve modification has a relative crystallinity of less than 10% and / or a microporous specific surface area of ​​less than 100 μm for the Y-type molecular sieve. 2 / g. This can prevent adverse effects on crystallinity, resulting in synthesized SAPO molecular sieves with high crystallinity.

[0017] The temperature for the primary activation with high-temperature steam is 500–700°C, and the activation time is 2–4 hours. The steam is preferably 100% by volume steam.

[0018] According to the present invention, the inorganic acid in step (2) is one or more of phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid.

[0019] According to the present invention, the pH value of the mixture formed by adding inorganic acid to the glue residue after primary activation is preferably 0.1 to 2, for example 0.5 to 2.0, the temperature of secondary activation is preferably 80 to 120°C, for example 85 to 99°C, and the time of secondary activation is preferably 1 to 24 hours, for example 5 to 15 hours.

[0020] The solid content of the secondary activated slurry is preferably 5-25% by weight.

[0021] The activated residue can be mixed with water to form a slurry, and then an inorganic acid can be added for secondary activation.

[0022] According to the present invention, the molar ratio of Al2O3, H3PO4, SiO2, template agent and H2O in the mixture in step (3) is 1.0:1.5~2.5:0~1.5:1~5:30~100; wherein Al2O3 is the number of moles of aluminum in the mixture converted to Al2O3, H3PO4 is the number of moles of phosphorus in the mixture converted to H3PO4, and SiO2 is the number of moles of silicon in the mixture converted to SiO2.

[0023] Preferably, the ratio of H3PO4 to Al2O3 is 1.8–2.2:1, the ratio of SiO2 to Al2O3 is 0.6–1.0:1, the ratio of template agent to Al2O3 is 1.5–3.5:1, and the ratio of H2O to Al2O3 is 40–60:1; the ratios are molar ratios.

[0024] Preferably, the silicon and aluminum introduced by the slag, based on oxides, account for 1 to 30% by weight, for example 5 to 25% by weight, of the total amount of phosphorus, silicon and aluminum in the mixture, wherein silicon is calculated as SiO2, aluminum as Al2O3 and phosphorus as P2O5.

[0025] According to the present invention, the supplementary silicon source in step (3) is one or more of silica sol, silica gel, and water glass; the supplementary aluminum source is one or more of boehmite, boehmite, alumina, aluminum hydroxide, aluminum sol, or soluble aluminum salt, preferably boehmite; the supplementary phosphorus source is at least one of phosphoric acid, ammonium phosphate, phosphite, or soluble metal phosphate; the phosphoric acid is preferably phosphoric acid with a mass fraction of 75-85%, and the phosphorus source can be supplemented by adding concentrated phosphoric acid with a phosphoric acid concentration of 75-85%;

[0026] The template agent is, for example, one or more of tetraethylammonium hydroxide, triethylamine, diethylamine, or morpholine; preferably triethylamine.

[0027] According to the present invention, in step (4), the aging time is 0 to 20 hours, for example 0.5 to 20 hours; preferably 8 to 15 hours, and the room temperature is 10 to 30°C; after the aging is completed, the heating rate to the hydrothermal crystallization temperature is preferably 2 to 5°C / min.

[0028] According to one embodiment of the present invention, the pH value of the aged product in step (4) is preferably 2 to 9.

[0029] According to one embodiment of the present invention, the hydrothermal crystallization temperature is 150-250°C and the time is 16-48 hours; preferably, the hydrothermal crystallization temperature is 160-220°C and the hydrothermal crystallization time is 24-48 hours.

[0030] According to the present invention, after hydrothermal crystallization, the obtained crystallization liquid (or mixed colloid) is cooled, filtered, and washed to obtain SAPO-34 molecular sieve. In one embodiment, the washing is performed by washing with water until the pH value of the water after washing is 7-8.

[0031] This invention, through the above-described technical solution, enables the synthesis of SAPO-34 molecular sieves using resin residue. The SAPO-34 molecular sieve synthesized by the method of this invention exhibits high crystallinity.

[0032] The method provided by this invention utilizes resin residue as a partial silicon and aluminum source, which can reduce the raw material cost of SAPO-34 synthesis. Furthermore, this invention uses a single high-temperature calcination hydrothermal treatment to activate the silicon and aluminum sources in the resin residue while removing some anions. A secondary hydrothermal activation is then performed using inorganic acids, particularly phosphoric acid, which effectively activates the silicon and aluminum sources while also serving as a synthesis raw material. This method allows for efficient utilization of silicon and aluminum in the resin residue while minimizing the emission of impurity ions, resulting in a higher resin residue utilization rate and improved uniformity of the crystallized material.

[0033] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0034] Figure 1 XRD pattern of the product in Example 1

[0035] Figure 2 SEM image of the product in Example 1

[0036] Figure 3 SEM image of product 1 (comparative example)

[0037] Figure 4 XRD pattern of product 1 (Comparative Example) Detailed Implementation

[0038] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0039] The gum residue used in this example is waste gum residue obtained from wastewater generated during the production of catalytic cracking catalysts, through processes such as sedimentation, filtration, and slag cutting.

[0040] The solid content of rubber residue #1 is 80% by weight. Based on the dry weight of the rubber residue, it contains 0.17% by weight Na₂O, 49% by weight Al₂O₃, 43.9% by weight SiO₂, and 3.18% by weight RE₂O₃; the relative crystallinity of the Y-type molecular sieve is 5%, and the micropore specific surface area is 47 μm. 2 / g of molecular sieve hydrothermal modification process slag provided by Qilu Branch of China Petrochemical Catalyst Co., Ltd.

[0041] The solid content of rubber residue #2 is 80% by weight. Based on the dry weight of the rubber residue, it contains 2.7% by weight Na₂O, 58.5% by weight Al₂O₃, 28.9% by weight SiO₂, and 6.71% by weight RE₂O. 3, Y-type molecular sieve has a relative crystallinity of 3% and a micropore specific surface area of ​​26 μm. 2 / g; Gel residue from the hydrothermal modification process of molecular sieves provided by Qilu Branch of China Petroleum & Chemical Corporation Catalyst Co., Ltd.

[0042] The solid content of rubber residue #3 is 80% by weight. Based on the dry weight of the rubber residue, it contains 5.82% by weight Na₂O, 31.6% by weight Al₂O₃, 54.7% by weight SiO₂, and 4.90% by weight RE₂O. 3， Y-type molecular sieve has a relative crystallinity of 8% and a micropore specific surface area of ​​74 μm. 2 / g; Gel residue from the gas-phase ultrastable modification process of molecular sieves provided by Qilu Branch of Sinopec Catalyst Co., Ltd.

[0043] The pseudoboehmite was produced by Shandong Aluminum Plant, with a solid content of 62.0% by weight.

[0044] The aluminum sol contains 21.5% aluminum oxide by weight and is produced by Sinopec Catalyst Co., Ltd. Qilu Branch.

[0045] Phosphoric acid was produced by Beijing Chemical Plant, and was of analytical grade with a mass concentration of 85%.

[0046] Sulfuric acid, produced by Beijing Chemical Plant, is of analytical grade and has a mass concentration of 98%.

[0047] Hydrochloric acid, produced by Beijing Chemical Plant, is of analytical grade and has a mass concentration of 36%.

[0048] The composition of the samples was determined by X-ray fluorescence spectroscopy (XRF).

[0049] The relative crystallinity of the sample was determined by X-ray powder diffraction (XRD).

[0050] SAPO-34 molecular sieve standard, produced by Sinopec Catalyst Co., Ltd. Nanjing Branch.

[0051] SAPO-34 molecular sieve relative crystallinity analysis method: taking the crystallinity of the standard sample as 100%, the peak areas of the diffraction peaks at 2θ = 9.6° and 20.8° in the XRD spectrum are fitted, and the relative crystallinity of the sample is obtained by the ratio of the sum of the peak areas of the two diffraction peaks of the synthetic sample to the sum of the peak areas of the two corresponding peaks of the standard sample.

[0052] The crystallinity of the Y-type molecular sieve with slag was analyzed using the method Q / SH 361 711-2017.

[0053] Preparation Example 1

[0054] Example 1

[0055] (1) 12.46g of glue residue No. 1 was activated for 3 hours at 550℃ by passing 100% water vapor through it.

[0056] (2) The activated slag was pulped in 89.33g of deionized water, 15g of phosphoric acid was added, the pH value was 1.9, and hydrothermal activation was carried out at 90℃ for 8h to obtain the slag slurry after secondary activation.

[0057] (3) Add 7.18g of boehmite, 11.84g of phosphoric acid and 14.19g of ethylenediamine to the above-mentioned secondary activated slurry to prepare a mixed solution;

[0058] (4) After the mixture is aged at 30℃ for 8 hours, it is heated to carry out hydrothermal crystallization at a rate of 5℃ / min. After being heated to 170℃, it is crystallized for 28 hours to obtain the crystallized solution.

[0059] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0060] Example 2

[0061] (1) Activate 10.56g of glue residue No. 1 by passing 100% water vapor at 650℃ for 3h.

[0062] (2) The glue residue after the first activation was slurried in 86.72g of deionized water, 2g of hydrochloric acid and 20g of phosphoric acid were added, the pH was 0.8, and the glue residue was hydrothermally activated at 90℃ for 8h to obtain the glue residue slurry after the second activation.

[0063] (3) Add 7.74g of boehmite, 6g of phosphoric acid and 18.98g of triethylamine to the above-mentioned secondary activated slurry to prepare a mixed solution;

[0064] (4) After the mixture is aged at room temperature (30℃, the same below) for 10 hours, it is heated to carry out hydrothermal crystallization at a heating rate of 2℃ / min. After reaching 170℃, it is crystallized for 32 hours to obtain crystallized solution.

[0065] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0066] Example 3

[0067] (1) 13.06g of No.1 rubber residue was activated once by passing 100% water vapor at 600℃ for 3h;

[0068] (2) The activated sludge was pulped in 96.31g of deionized water, and 2g of sulfuric acid and 15g of phosphoric acid were added. The pH was 0.8. The mixture was then hydrothermally activated at 90℃ for 8h to obtain a dispersion of the sludge after secondary activation.

[0069] (3) Add 7.56g of boehmite, 6.09g of phosphoric acid and 12.01g of isopropylamine to the above-mentioned secondary activated gel residue dispersion to prepare a mixed solution;

[0070] (4) After the mixed solution is aged at room temperature for 8 hours, it is heated to carry out hydrothermal crystallization at a heating rate of 3℃ / min to 190℃ and then crystallized for 24 hours to obtain the crystallized solution.

[0071] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0072] Example 4

[0073] (1) Activate 21.1g of glue residue No. 2 by passing 100% water vapor at 600℃ for 3h;

[0074] (2) The gel residue after the first activation was slurried in 95.12g of deionized water, and 2g of sulfuric acid and 15g of phosphoric acid were added. The pH was 1.2. The gel residue was hydrothermally activated at 90℃ for 8h to obtain a dispersion of gel residue after the second activation.

[0075] (3) Add 0.68g of boehmite, 6.09g of phosphoric acid and 12.01g of isopropylamine to the above-mentioned secondary activated slag dispersion to prepare a mixed solution;

[0076] (4) After the mixed solution is aged at room temperature for 8 hours, it is heated to carry out hydrothermal crystallization. The heating rate is 3℃ / min. After crystallization at 190℃ for 24 hours, the crystallized solution is obtained.

[0077] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0078] Example 5

[0079] (1) 11.15g of rubber residue No. 3 was activated once by passing 100% water vapor at 600℃ for 3h to obtain rubber residue after one activation;

[0080] (2) The gel residue after the first activation was slurried in 95.36g of deionized water, and 2g of sulfuric acid and 15g of phosphoric acid were added. The pH was 0.9. The gel residue was then hydrothermally activated at 90℃ for 8h to obtain a dispersion of gel residue after the second activation.

[0081] (3) Add 10.39g of boehmite, 6.09g of phosphoric acid and 12.01g of isopropylamine to the above-mentioned secondary activated slag dispersion to prepare a mixed solution;

[0082] (4) After the mixture is aged at room temperature for 8 hours, it is heated to perform hydrothermal crystallization. The heating rate is 3℃ / min to 190℃ and then crystallization is carried out for 24 hours to obtain the crystallized liquid.

[0083] (5) The crystallization solution is cooled, washed, filtered and dried to obtain SAPO-34 molecular sieve.

[0084] Comparative Example 1

[0085] (1) Add 12.46g of glue residue No. 1 to 91.83g of deionized water and beat for 3 hours to obtain glue residue slurry;

[0086] (2) Add 7.18g of boehmite, 26.84g of phosphoric acid and 14.19g of ethylenediamine to the above-mentioned slurry to prepare a mixed solution.

[0087] (3) After the mixture is aged at room temperature for 8 hours, it is heated to 170℃ for hydrothermal crystallization at a heating rate of 5℃ / min, and then crystallized for 28 hours to obtain the crystallized solution.

[0088] (4) The crystallization solution is cooled, washed, filtered and dried to obtain DB-1.

[0089] Comparative Example 2

[0090] 21.1g of slag #2 was calcined at 800℃ for 3 hours to obtain activated slag. Aluminum source, phosphorus source, and template agent were added according to the proportions in Example 4. After aging and crystallization, the slag was cooled, washed, filtered, and dried to obtain product DB-2.

[0091] Comparative Example 3

[0092] 11.15g of glue residue #3 and sodium hydroxide were mixed evenly at a mass ratio of 1:1.1 and calcined at 700℃ for 3 hours to obtain activated glue residue. The residue was washed with deionized water. The product contained 5.5 wt% Na₂O, 32.9 wt% Al₂O₃, 55.7 wt% SiO₂, and 5.2 wt% RE₂O₃. Phosphorus and aluminum sources were added according to the proportions in Example 5, and a template agent was added. After aging and crystallization, the residue was cooled, washed, filtered, and dried to obtain DB-3.

[0093] The sample properties of the above embodiments and comparative examples are shown in Table 1.

[0094] Table 1 Crystallinity Analysis of Samples

[0095] Sample source Relative crystallinity, % Example 1 89.5 Example 2 84.3 Example 3 85.1 Example 4 86.7 Example 5 84.9 Comparative Example 1 12.1 Comparative Example 2 13.4 Comparative Example 3 14.9

[0096] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0097] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0098] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for synthesizing SAPO-34 molecular sieve using slag produced from catalytic cracking catalysts, comprising the following steps: (1) The slag is activated by high-temperature steam once to obtain slag after one activation; wherein, based on the dry weight of the slag, the slag contains 0-9% by weight of Na2O, 20-60% by weight of Al2O3, 20-60% by weight of SiO2, and 0-15% by weight of RE2O3; the slag has a relative crystallinity of less than 10% for Y-type molecular sieves and / or a micropore specific surface area of ​​less than 100 μm. 2 / g; (2) Add inorganic acid to the activated slag after one activation and perform a second hydrothermal activation to obtain a slag slurry after two activations; (3) After secondary activation, aluminum source, optional silicon source, phosphorus source and template agent are added to the glue residue slurry to obtain a mixed solution; (4) After the mixture is aged by stirring at room temperature, it is heated to carry out hydrothermal crystallization to obtain a crystallized solution; (5) The crystallization solution is cooled, washed, filtered and dried.

2. The method according to claim 1, characterized in that, The sludge is molecular sieve modified sludge, and the molecular sieve modification includes steam treatment and / or treatment with fumed silicon tetrachloride, washing, and optional exchange.

3. The method according to claim 1, characterized in that, The temperature for the primary activation with high-temperature steam is 500–700°C, and the activation time is 2–4 hours. The steam used is 100% by volume steam.

4. The method according to claim 1, characterized in that, The inorganic acid mentioned in step (2) is one or a mixture of several of phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid.

5. As described in claim 1, characterized in that, The pH value of the mixture formed by adding inorganic acid to the glue residue after the first activation is 0.1 to 2, the temperature of the second activation is 80 to 120°C, and the time is 1 to 24 hours; the solid content of the glue residue slurry after the second activation is 5 to 25% by weight.

6. The method according to claim 1, characterized in that, In step (3), the molar ratio of Al2O3, H3PO4, SiO2, template agent and H2O in the mixture is 1:1.5~2.5:0~1.5:1~5:30~100; wherein Al2O3 is the number of moles of aluminum in the mixture converted to Al2O3, H3PO4 is the number of moles of phosphorus in the mixture converted to H3PO4, and SiO2 is the number of moles of silicon in the mixture converted to SiO2.

7. The method according to claim 6, characterized in that, In the mixture described in step (3), the ratio of H3PO4 to Al2O3 is 1.8–2.2:1, the ratio of SiO2 to Al2O3 is 0.6–1.0:1, the ratio of template agent to Al2O3 is 1.5–3.5:1, and the ratio of H2O to Al2O3 is 40–60:1; the ratios are molar ratios. In terms of oxides, the silicon and aluminum introduced by the slag account for 1 to 30% by weight of the total phosphorus, silicon and aluminum in the mixture, where silicon is calculated as SiO2, aluminum as Al2O3 and phosphorus as P2O5.

8. The method according to claim 1, characterized in that, The silicon source mentioned in step (3) is one or more of silica sol, silica gel, and water glass; The aluminum source in step (3) is one or more of boehmite, boehmite, alumina, aluminum hydroxide, aluminum sol, or soluble aluminum salt. The phosphorus source in step (3) is at least one of phosphoric acid, ammonium phosphate, phosphite, or soluble metal phosphate; The template agent is one or more of tetraethylammonium hydroxide, triethylamine, diethylamine, or morpholine.

9. The method according to claim 8, characterized in that, The aluminum source in step (3) is boehmite; the phosphorus source is phosphoric acid with a mass fraction of 75-85%; and the template agent is triethylamine.

10. The method according to claim 1, characterized in that, In step (4), the aging time is 0 to 20 hours; the room temperature is 10 to 30 degrees Celsius; after aging, the heating rate to the hydrothermal crystallization temperature is 2 to 5 degrees Celsius / min.

11. The method according to claim 1, characterized in that, The pH value of the aged product in step (4) is 2 to 9; in step (4), the aging time is 8 to 15 hours.

12. The method according to claim 1 or 8, characterized in that, The hydrothermal crystallization temperature is 150–250℃, and the time is 16–48 hours.

13. The method according to claim 12, characterized in that, The hydrothermal crystallization temperature is 160–220°C, and the hydrothermal crystallization time is 24–48 hours.

14. The method according to claim 1, characterized in that, After hydrothermal crystallization, the resulting crystallization solution is cooled, filtered, and washed to obtain SAPO-34 molecular sieve.

15. The method according to claim 1, characterized in that, The washing process involves rinsing with water until the pH of the water after washing is 7-8.

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