Method for in-situ synthesis of encapsulated metal catalysts with ligand-stabilized seeds

Abstract

The application relates to a synthesis method of a TON type molecular sieve encapsulated metal catalyst. The method specifically implements the following steps: after TON type molecular sieves, organic amine, a silicon source, an aluminum source, potassium hydroxide, a metal precursor, an amine ligand and water are fully mixed, crystallization is carried out by heating for a certain time, washing, drying and calcination are carried out, and the TON type molecular sieve encapsulated metal catalyst is prepared. The method provided by the application can prepare a pure silicon and aluminum-containing TON type molecular sieve encapsulated Pt catalyst, and the TON type molecular sieve encapsulated Pt catalyst has great application potential in the fields of coal chemical industry and petroleum chemical industry. The synthesis method provided by the application is low in cost, simple in operation and safe.

Description

Technical Field

[0001] This invention relates to a method for synthesizing TON-type molecular sieve-encapsulated metal catalysts, specifically a method for in-situ synthesis of TON-type molecular sieve-encapsulated metal catalysts assisted by amine ligand-stabilized metal seed crystals. Background Technology

[0002] Metal-supported catalysts are an important class of catalysts, playing a crucial role in many important industrial processes. The size of the metal particles affects the exposure of metal sites on the particle surface, which is critical to the catalytic performance of the metal particles. However, metal particles on supports are prone to aggregation and sintering under actual reaction conditions, a common problem with many oxide and carbon supports. To address this issue, metal particles can be encapsulated within porous materials. The framework of the porous material confines the metal particles, inhibiting aggregation and sintering. Molecular sieves, with their abundant pore structure, are effective supports for encapsulating metal particles.

[0003] Kegnaes et al. encapsulated Au within the mesopores of pure silicon Silicalite-1 (Angew. Chem. Int. Ed., 2014, 53, 12513-12516.); Iglesia et al. encapsulated noble metals within the α-cages of LTA-structured molecular sieves (J. Catal., 2014, 311, 458-468.; J. Catal., 2016, 342, 3370-3376.); Corma et al. encapsulated Pt within MC The supercage and twelve-membered ring "cup" structure on the outer surface of M-22 molecular sieve (Nat. Mater., 2017, 16, 132-138.); Yu Jihong et al. reported encapsulating Rh in the five-membered ring of MFI molecular sieve (Angew. Chem. Int. Ed., 2019, 58, 18570-18576.); Xiao Fengshou et al. encapsulated AuPd alloy inside ZSM-5 molecular sieve crystal (Science, 2020, 367, 193-197.).

[0004] Wang Jun et al. (ACS Appl. Mater. Interfaces, 12, 2020, 11522-11532.) reported a method for encapsulating Pt within pure silicon TON-type molecular sieve crystals. The Pt precursor, generated by the reaction of 3-mercaptopropyltrimethoxysilane with chloroplatinic acid, was hydrolyzed together with tetraethyl orthosilicate under acidic conditions. An ionic liquid template agent and sodium hydroxide solution were added, and the resulting product was evaporated and dried. The resulting dry gel was then subjected to heating and crystallization to obtain the pure silicon TON-type molecular sieve-encapsulated Pt catalyst.

[0005] The aforementioned research on zeolite-encapsulated metal catalysts focuses on the preparation of metal catalysts encapsulated in pure silicon TON-type zeolites with cage-like, cross-channel, or one-dimensional straight-channel structures, but does not address the preparation of metal catalysts encapsulated in aluminum-containing TON-type zeolites. Furthermore, the preparation process of pure silicon TON-type zeolite-encapsulated metal catalysts is complex, requiring expensive ionic liquid template agents, resulting in high synthesis costs. Therefore, this invention provides a novel method for synthesizing TON-type zeolite-encapsulated metal catalysts, requiring only the addition of a metal precursor, amine ligands, and the TON-type zeolite during the TON-type zeolite synthesis process. The method provided by this invention can synthesize both pure silicon and aluminum-containing TON-type zeolite-encapsulated metal catalysts, with low synthesis costs and simple operation. Summary of the Invention

[0006] In view of the current research status, the present invention aims to provide a low-cost and simple method for synthesizing TON-type molecular sieve-encapsulated metal catalysts.

[0007] This invention enables the preparation of metal catalysts encapsulated in TON-type molecular sieves by adding metal precursors, amine ligands, and TON-type molecular sieves during the synthesis process.

[0008] Specifically, the method for preparing TON-type molecular sieve-encapsulated metal catalysts provided by the present invention comprises the following steps:

[0009] 1) Aluminum source, organic amine, silicon source, metal precursor, amine ligand, water, and potassium hydroxide are mixed in a certain proportion and stirred evenly to form mixture A. The molar ratio of SiO2:Al2O3:K2O:organic amine:H2O in mixture A is 0.4~5:0.01:0.01~2:0.01~1:10~80 (silicon source, aluminum source, and potassium hydroxide are calculated according to their oxide forms). The obtained mixture A is heated and crystallized at 80~200℃ for 6h~72h. After cooling to room temperature, it is filtered, washed, and dried. The obtained solid product is uncalcined TON type molecular sieve. The obtained uncalcined TON type molecular sieve is calcined at 300~800℃ for 4h~36h. The obtained solid product is calcined TON type molecular sieve.

[0010] 2) Mix calcined or uncalcined TON-type molecular sieve, aluminum source, organic amine, silicon source, metal precursor, amine ligand, water, and potassium hydroxide in a certain proportion and stir evenly to form mixture B. The molar ratio of SiO2:Al2O3:K2O:organic amine:H2O in mixture B is 0.4~5:0.01:0.01~2:0.01~1:10~80 (silicon source, aluminum source, and potassium hydroxide are calculated according to their oxide forms). The amount of metal precursor is 0.01wt.%~15wt.% (mass percentage of elemental metal and SiO2 in silicon source). The molar ratio of amine ligand to metal precursor is 1:1~300. The amount of TON-type molecular sieve is 0.1wt.%~50wt.% (mass percentage of molecular sieve and SiO2 in silicon source).

[0011] 3) The mixture B was heated and crystallized at 80-180℃ for 6-72 hours. After cooling to room temperature, it was filtered, washed, dried, and calcined at 300-800℃ for 4-36 hours. The resulting solid product was a TON-type molecular sieve encapsulated metal catalyst.

[0012] In the method described, the silicon source in steps 1) and 2) is one or more of water glass, tetraethyl orthosilicate, silica, and silica sol.

[0013] In the method described, the aluminum source in steps 1) and 2) is one or more of aluminum sulfate, aluminum isopropoxide, sodium aluminate, aluminum nitrate, and boehmite.

[0014] In the method, the organic amine in steps 1) and 2) is one or more of 1,8-octanediamine, ethanolamine, diethylamine, 1,6-hexanediamine or 1-butanediamine.

[0015] In the method, the molar ratio of SiO2:Al2O3:organic amine:K2O:H2O in mixture A in steps 1) and 2) is 0.4-5:0.01:0.01-2:0.01-1:10-80;

[0016] In the method described, in step 2), the amount of metal precursor is 0.01 wt.% to 10 wt.%, the molar ratio of amine ligand to metal precursor is 1:1 to 300, and the amount of TON-type molecular sieve is 0.1 wt.% to 30 wt.%.

[0017] In the method, the metal precursor in step 2) is one or more of the following: tetraammineplatinum(II), tetraammineplatinum(II), chloroplatinic acid, diethylenediamineplatinum(II), and platinum(II) chloride.

[0018] In the method, the amine ligand in step 2) is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine;

[0019] In the method described in step 3), the preferred crystallization temperature of mixture A is 120℃~170℃, and the preferred crystallization time is 24h~72h.

[0020] In the method described in step 3), the preferred roasting temperature is 350℃~650℃, and the preferred roasting time is 6h~24h.

[0021] During the heating and crystallization process, amine ligands protect the metal from precipitation, while TON-type molecular sieves act as seed crystals to promote the crystallization of TON-type molecular sieves.

[0022] Compared with the pure silicon TON-type molecular sieve-encapsulated metal catalysts synthesized by existing technologies, the synthesis method of the TON-type molecular sieve-encapsulated metal catalyst of the present invention has the following characteristics:

[0023] (1) A new method for synthesizing metal catalysts encapsulated in pure silicon TON molecular sieves is provided.

[0024] (2) This synthesis method is simple and easy to implement. It only requires adding metal precursors, amine ligands and TON-type molecular sieves during the molecular sieve synthesis process, and then heating and crystallizing to obtain TON-type molecular sieve-encapsulated metal catalysts.

[0025] Compared with existing technologies for synthesizing TON-type molecular sieve-encapsulated metal catalysts, the synthesis method of the TON-type molecular sieve-encapsulated metal catalyst of the present invention has the following characteristics:

[0026] (1) A method for synthesizing metal catalysts encapsulated in aluminum-containing TON-type molecular sieves is provided.

[0027] (2) The aluminum-containing TON-type molecular sieve synthesized by this method has both metal sites and acid sites, which can expand the application of TON-type molecular sieve encapsulated metal catalysts in bifunctional catalytic reactions such as cracking and isomerization. Attached Figure Description

[0028] Figure 1 This is a TEM image of the sample obtained in Comparative Example 1 of this invention;

[0029] Figure 2 This is a TEM image of the sample obtained in Comparative Example 2 of this invention;

[0030] Figure 3 This is a TEM image of the sample obtained in Comparative Example 3 of this invention;

[0031] Figure 4 These are TEM images of the samples obtained in Example 7 of this invention; Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but it should be noted that the content of the present invention is not limited thereto.

[0033] Comparative Example 1

[0034] In this comparative example, a Pt / TON catalyst with a Pt loading of 0.1 wt.% was prepared by the conventional impregnation method, and the anti-sintering ability of the catalyst under calcination conditions of 550 °C was investigated.

[0035] 1) Synthesis of TON-type molecular sieves using a hydrothermal method:

[0036] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Next, add 0.9g of TON-type molecular sieve and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain the TON-type molecular sieve.

[0037] 2) A Pt / TON catalyst with a Pt loading of 0.1 wt.% was prepared using the conventional impregnation method, and its resistance to sintering under calcination conditions at 550 °C was investigated.

[0038] TON-type molecular sieves were pressed into tablets and crushed and sieved to form particles of 20–40 mesh. Then, a chloroplatinic acid solution with a Pt content of 0.038 g / mL was added dropwise. The ratio of TON-type molecular sieve to chloroplatinic acid solution was 1 g TON-type molecular sieve : 0.5 mL chloroplatinic acid solution. The resulting mixture was transferred to an oven and dried at 100 °C, followed by calcination at 550 °C for 12 h to obtain the impregnated Pt / TON catalyst. The Pt dispersion and average particle size of the samples, measured by CO chemisorption, are summarized in Table 1. TEM images of the samples are shown below. Figure 1 As shown: Pt particles with a diameter of approximately 10 nm are located on the outer surface of the TON-type molecular sieve.

[0039] Comparative Example 2

[0040] In this comparative example, a Pt / TON catalyst with a Pt loading of 0.1 wt.% was prepared by electrostatic adsorption, and the anti-sintering ability of the catalyst under calcination conditions of 550 °C was investigated.

[0041] 1) Preparation of TON-type molecular sieves using a hydrothermal method:

[0042] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Next, add 0.9g of TON-type molecular sieve and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain the TON-type molecular sieve.

[0043] 2) A Pt / TON catalyst with a Pt loading of 0.1 wt.% was prepared by electrostatic adsorption, and its resistance to sintering under calcination conditions at 550 °C was investigated.

[0044] The prepared TON-type molecular sieve was dispersed in an ammonia solution with pH=11. After thorough stirring, a dichlorotetraammineplatinum(II) solution (Pt content 0.02 g / mL) was added dropwise and stirred for 1 h. The ratio of TON-type molecular sieve, ammonia solution, and dichlorotetraammineplatinum(II) solution was 1 g TON-type molecular sieve : 50 mL ammonia solution : 0.5 mL dichlorotetraammineplatinum(II) solution. The resulting mixture was then filtered, washed, dried in an oven at 100 °C, and calcined at 550 °C for 12 h to obtain the Pt / TON catalyst supported by electrostatic adsorption. The Pt dispersion and average particle size of the samples measured by CO chemisorption are summarized in Table 1. TEM images of the samples are shown below. Figure 2 As shown: Pt particles with a diameter of 4-10 nm are located on the outer surface of TON type molecular sieve.

[0045] Comparative Example 3

[0046] In this comparative example, a Pt catalyst encapsulated with TON molecular sieve with a Pt loading of 0.1 wt.% was prepared by in-situ synthesis. No calcined or uncalcined TON molecular sieve was added during the preparation process, and the anti-sintering ability of the catalyst under calcination conditions of 550℃ was investigated.

[0047] Weigh 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 5g ethylenediamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, stir thoroughly, and then add 45g of 40% silica sol. After stirring evenly, transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in a 160℃ oven for 3 days, cool to room temperature, wash with deionized water, and dry in a 100℃ oven. After calcination at 550℃ for 12 hours, a TON-type molecular sieve-encapsulated Pt catalyst is obtained. The Pt dispersion and average particle size measured by CO chemisorption are summarized in Table 1. TEM images of the samples are shown below. Figure 3As shown, the Pt particles have a diameter of approximately 50 nm and are located on the outer surface of the TON-type molecular sieve, indicating that a TON-type molecular sieve-encapsulated Pt catalyst cannot be prepared without the addition of the TON-type molecular sieve during the synthesis process.

[0048] Example 1

[0049] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0050] Weigh 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 5g ethylenediamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, and stir thoroughly. Next, add 45g of silica sol with a mass concentration of 40%, and stir evenly. Then add 1.8g of TON-type molecular sieve, and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcining at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0051] Example 2

[0052] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0053] Weigh 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 8.6g diethylenetriamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, and stir thoroughly. Next, add 45g of 40% silica sol, and stir evenly. Then add 1.8g of TON-type molecular sieve, and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcination at 550℃ for 12 hours, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0054] Example 3

[0055] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0056] Weigh 5.1g potassium hydroxide, 8.7g 1,6-hexanediamine, and 12.1g triethylenetetramine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, and stir thoroughly. Next, add 45g of 40% silica sol, stir evenly, and then add 1.8g of TON-type molecular sieve. After stirring thoroughly, transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcining at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0057] Example 4

[0058] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0059] Weigh 5.1g of potassium hydroxide, 8.7g of 1,6-hexanediamine, and 15.7g of tetraethylenepentamine, add 200g of water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, stir thoroughly, add 45g of 40% silica sol, stir evenly, and then add 1.8g of TON-type molecular sieve. After stirring thoroughly, transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcining at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0060] Example 5

[0061] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0062] Weigh out 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 14.8g N,N'-bis(3-aminopropyl)ethylenediamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, stir thoroughly, add 45g of 40% silica sol, stir evenly, and then add 1.8g of TON-type molecular sieve. After stirring thoroughly, transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcining at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0063] Example 6

[0064] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0065] Weigh 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 8.7g N-(2-hydroxyethyl)ethylenediamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, stir thoroughly, add 45g of 40% silica sol, stir evenly, and then add 1.8g of TON-type molecular sieve. After stirring thoroughly, transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in an oven at 160℃ and keep it there for 3 days. After cooling to room temperature, wash with deionized water and dry in an oven at 100℃. After calcination at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained.

[0066] Example 7

[0067] Weigh 4.5g of 1,6-hexanediamine, 2.5g of potassium hydroxide, and 1.1g of aluminum sulfate. Add 100g of water and stir until homogeneous. Then add 20g of 40% silica sol and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene and place it in a 160℃ oven for 3 days. After cooling to room temperature, wash with deionized water and dry in a 100℃ oven. Calcine at 550℃ for 12 hours to obtain TON-type molecular sieve.

[0068] Weigh 5.1g potassium hydroxide, 2g aluminum sulfate, 8.7g 1,6-hexanediamine, and 5g ethylenediamine, add 200g water, and stir thoroughly. Then add 4.7mL of chloroplatinic acid solution with a Pt content of 0.038g / mL, and stir thoroughly. Next, add 45g of 40% silica sol, and stir evenly. Then add 1.8g of pure silicon TON-type molecular sieve, and stir thoroughly. Transfer the mixture to a stainless steel reactor lined with polytetrafluoroethylene, place it in a 160℃ oven, keep it in the oven for 3 days, cool to room temperature, wash with deionized water, and dry in a 100℃ oven. After calcination at 550℃ for 12h, the TON-type molecular sieve-encapsulated Pt catalyst is obtained. The Pt dispersion and average particle size measured by CO chemical adsorption are summarized in Table 1. TEM images of the samples are shown below. Figure 4 As shown: Pt particles with a diameter of approximately 1 nm are encapsulated inside a TON-type molecular sieve.

[0069] Example 8

[0070] The catalysts prepared in Comparative Examples 1, 2, 3, and 7 were used for propane dehydrogenation in a fixed-bed reactor with an inner diameter of 8 mm. The steps were as follows: 8 g of quartz sand was loaded into the bottom of a quartz tube, and the catalyst was prepared into particles of 20–40 mesh. 0.71 g of catalyst particles were loaded into a stainless steel tube, and then 7 g of quartz sand was loaded into the stainless steel reaction tube. Before the catalytic reaction began, the catalyst was reduced in the reaction tube at 550 °C for 1 h, with a hydrogen flow rate of 34 mL / min. The reaction gas (volume composition) introduced during the reaction was 50% C3H8 / H2, the reaction gas flow rate was 68 mL / min, and the reaction temperature was 550 °C.

[0071] The propane dehydrogenation reaction results were as follows: the propane conversion rates of the catalysts prepared in Comparative Examples 1, 2, and 3 were 24%, 31%, and 15%, respectively. After 9 hours of reaction, the propane conversion rates decreased to 5%, 7%, and 3%, respectively, indicating a significant decrease in catalyst activity. The catalyst prepared in Example 7 had a propane conversion rate of 40%, and after 9 hours of reaction, the conversion rate still reached 35%, with no significant decrease in catalyst activity. The propane dehydrogenation results show that the catalyst prepared in Example 7 maintains high catalytic activity under high-temperature reaction conditions and exhibits excellent anti-sintering ability, while the catalysts prepared in Comparative Examples 1, 2, and 3 rapidly deactivated under high-temperature reaction conditions, indicating poor anti-sintering ability.

[0072] The method provided by this invention can prepare TON-type molecular sieve-encapsulated Pt catalysts containing aluminum and pure silicon. The prepared TON-type encapsulated Pt catalysts exhibit excellent anti-sintering ability and have application potential in petrochemical, coal chemical, and other fields. The synthesis method provided by this invention is low-cost, simple, and safe to operate.

[0073] Table 1 shows the dispersity and average particle size of Pt in the comparative and example samples determined by CO chemisorption.

[0074] Sample Example No. Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 7 Pt Dispersion (%) 12.5 27.5 3.9 54.2 Pt Average Particle Size (nm) 9.0 4.1 29.2 2.1

Claims

1. A method for in-situ synthesis of molecular sieve-encapsulated metal catalysts assisted by ligand-stabilized seed crystals, characterized in that: Using amine ligands as stabilizers, a TON-type molecular sieve-encapsulated metal catalyst was synthesized using TON-type molecular sieves, organic amines, potassium hydroxide, silicon source, aluminum source, and metal precursors. The synthesis process included: 1) Mix aluminum source, organic amine, silicon source, water, and potassium hydroxide, and stir evenly to form mixture A. The molar ratio of SiO2: Al2O3: K2O: organic amine: H2O in mixture A is calculated according to their oxide forms as 0.4~5: 0.01: 0.01~2: 0.01~1: 10~80. The obtained mixture A is heated and crystallized at 80~200℃ for 6h~72h. After cooling to room temperature, it is filtered, washed, and dried. The solid product obtained is uncalcined TON type molecular sieve. The uncalcined TON molecular sieve was calcined at 300~800℃ for 4h~36h to obtain the solid product, which is the calcined TON molecular sieve. 2) Mix calcined or uncalcined TON-type molecular sieve, aluminum source, organic amine, silicon source, metal precursor, amine ligand, water, and potassium hydroxide, and stir until homogeneous to form mixture B. The silicon source, aluminum source, and potassium hydroxide are calculated based on their oxide forms. The molar ratio of SiO2:Al2O3:K2O:organic amine:H2O in mixture B is 0.4~5:0.01:0.01~2:0.01~1:10~80. The amount of metal precursor, calculated based on the mass percentage of SiO2 in the metal element and silicon source, is 0.01wt.%~15wt.%, the molar ratio of amine ligand to metal precursor is 1:1~300, and the amount of TON-type molecular sieve, calculated based on the mass percentage of SiO2 in the molecular sieve and silicon source, is 0.1wt.%~50wt.%. 3) The prepared mixture B is heated and crystallized at 80~180℃ for 6h~72h, cooled to room temperature, filtered, washed, dried, and calcined at 300~800℃ for 4h~36h. The obtained solid product is a TON-type molecular sieve encapsulated metal catalyst. In steps 1) and 2), the organic amine is one or more of 1,8-octanediamine, ethanolamine, diethylamine, 1,6-hexanediamine or 1-butanediamine. In step 2), the amine ligand is one or more of ethylenediamine, N,N'-bis(3-aminopropyl)ethylenediamine, N-(2-hydroxyethyl)ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine.

2. The synthesis method according to claim 1, characterized in that: In steps 1) and 2), the silicon source is one or more of water glass, tetraethyl orthosilicate, silica, and silica sol.

3. The synthesis method according to claim 1, characterized in that: In steps 1) and 2), the aluminum source is one or more of aluminum sulfate, aluminum isopropoxide, sodium aluminate, aluminum nitrate, and boehmite.

4. The synthesis method according to claim 1, characterized in that: In steps 1) and 2), the molar ratio of SiO2:Al2O3:organic amine:K2O:H2O in mixtures A and B is 0.8~5:0.01:0.01~2:0.01~1:10~80.

5. The synthesis method according to claim 1, characterized in that: The amount of metal precursor is calculated from the mass percentage of SiO2 in the metal element and silicon source, and the molar ratio of amine ligand to metal precursor is 1:1~200. The amount of TON type molecular sieve is calculated from the mass percentage of SiO2 in the molecular sieve and silicon source, and the amount of TON type molecular sieve is 0.1wt.%~30wt.%.

6. The synthesis method according to claim 1, characterized in that: In step 2), the metal precursor is one or more of the following: tetraammineplatinum(II), tetraammineplatinum(II), chloroplatinic acid, diethylenediamineplatinum(II), and platinum(II) chloride.

7. The synthesis method according to claim 1, characterized in that: In step 2), the amine ligand is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

8. The synthesis method according to claim 1, characterized in that: In step 3), the crystallization temperature of mixture A is 120℃~170℃, and the crystallization time is 24h~72h.

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