MFI type heteroatom molecular sieve metal-coated composite catalytic material as well as preparation method and application thereof

Abstract

The embodiment of the invention provides an MFI type heteroatom molecular sieve metal-coated composite catalytic material as well as a preparation method and application thereof, and relates to the technical field of catalysis. The MFI type heteroatom molecular sieve metal-coated composite catalytic material has a hollow structure, and the composite catalytic material comprises the following components: an MFI type molecular sieve which is used as a basic carrier and has a specific topological structure; and the rare earth element heteroatom is doped in the molecular sieve framework and is selected from one or more of cerium and lanthanum. Electron transfer occurs, and adsorption and desorption of intermediate species are changed; the preparation method solves the problems that existing rare earth element atoms are large in radius and difficult to enter a framework, meanwhile, metal atoms in the framework can interact with the coated precious metal, the dispersity is improved, precious metal reduction is achieved, meanwhile, the high-temperature thermal stability is improved, and the service life is prolonged. And the MFI type heteroatom hollow coating structure can stabilize the noble metal at a high temperature, and shows a better reaction effect in methane catalytic oxidation.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, and in particular to an MFI type heteroatom molecular sieve metal-coated composite catalytic material, a preparation method and an application thereof. Background Art

[0002] The petroleum and organic chemical industry is the main source of volatile organic compounds (VOCs) emissions. Volatile organic compounds (VOCs) not only harm the environment, but also have strong irritation to human skin and mucous membranes, and are carcinogenic to humans and animals. In order to reduce the emission of volatile organic compounds, the state has formulated the "Law of the People's Republic of China on the Prevention and Control of Air Pollution" and issued GB16297-1996 "Comprehensive Emission Standards for Air Pollutants", which strictly stipulates the emission of 16 organic pollutants. Therefore, how to achieve VOCs emission reduction is a key scientific issue that needs to be solved urgently.

[0003] Natural gas is abundant in resources, has high calorific value and is environmentally friendly, and has been widely used in industries such as natural gas vehicles and gas turbines. Natural gas is mainly composed of methane, and direct emission will cause the greenhouse effect, so it needs to be effectively purified.

[0004] Currently, catalytic combustion is one of the main means of VOC treatment, which uses catalytic materials to degrade high-concentration VOCs into water and carbon dioxide. Methane catalytic oxidation is an important method for treating tail gas. By designing efficient catalytic materials to reduce the activation energy of CH bonds, methane can be fully converted under low temperature conditions, improving treatment efficiency and reducing secondary pollution.

[0005] MFI zeolite molecular sieve has the characteristics of surface-adjustable acidity, shape-selective catalysis, and good hydrothermal stability, and is a good carrier for loading metal active sites. Metal-modified MFI zeolite molecular sieve has dual functionality, in which the acid center and the metal component have a synergistic catalytic effect during the catalytic process, changing the catalytic activity and selectivity. At present, metal-doped MFI zeolite molecular sieve is a hot topic of research at home and abroad.

[0006] Direct hydrothermal synthesis is a commonly used method to introduce metals into molecular sieves. Through interaction forces such as van der Waals forces or electrostatic attraction, the interaction between the metal precursor and the molecular sieve is induced, inducing the metal nanoparticles to be embedded in the molecular sieve framework during the self-assembly process. Since the above process is carried out under strong alkali and high temperature hydrothermal conditions, it is easy to lead to the formation of metal hydroxides. In addition, the "dissolution-recrystallization" process induced by the subsequent alkali treatment process will cause the loss of some metal components. Therefore, how to strengthen the interaction between the carrier and the metal is the key to preparing metal-coated structures. Summary of the invention

[0007] According to an embodiment of the present invention, there is provided an MFI-type heteroatom molecular sieve metal-coated composite catalytic material, a preparation method and an application thereof, which are used to solve the problems existing in the above-mentioned background technology.

[0008] In the first aspect of the present invention, there is provided an MFI-type heteroatom molecular sieve metal-coated composite catalytic material.

[0009] The MFI-type heteroatom molecular sieve metal-coated composite catalytic material has a hollow structure, and the composite catalytic material includes the following components: The MFI-type molecular sieve, as a basic carrier, has a specific topological structure; Rare earth element heteroatoms, doped in the molecular sieve framework, selected from one or more of cerium and lanthanum; Noble metals, loaded on the molecular sieve, selected from one or more of palladium and platinum.

[0010] Preferably, the ratio of each component is as follows: Calculated by the total mass percentage of the catalyst, the content of the rare earth element heteroatoms is 0.5% to 5%; Calculated by the total mass percentage of the catalyst, the content of the noble metals is 0.05% to 0.4%; The atomic ratio of the noble metal to the rare earth element heteroatom is 0.06 to 0.60; The molar ratio of the rare earth element heteroatom to the organic ligand is 1:1 to 1:5.

[0011] In the second aspect of the present invention, there is provided a preparation method of an MFI-type heteroatom molecular sieve metal-coated composite catalytic material.

[0012] The method includes the following steps: S1. Using the hydrothermal synthesis method to prepare a gel substance, specifically including: i. Mix the silicon source, the organic template agent and deionized water, and stir until the silicon source is completely dissolved to obtain a first mixed solution; ii. Mix the cerium source and the organic ligand, add them to deionized water, and stir until completely dissolved to obtain a second mixed solution; iii. Add the second mixed solution to the first mixed solution and stir evenly. Whether to add an aluminum source can be selected according to the target product; Do not add an aluminum source to prepare a palladium / cerium-doped pure silicon molecular sieve; Add an aluminum source to prepare a palladium / cerium-doped silicon-aluminum molecular sieve; Continue to stir the prepared palladium / cerium-doped pure silicon molecular sieve or the palladium / cerium-doped silicon-aluminum molecular sieve for 1 to 24 hours to obtain a gel substance; S2. Transfer the gel substance into a sealed high-pressure reactor, and crystallize it at a temperature of 100-200 °C for 1-5 days; separate and collect the crystallization product, dry it, and then calcine it at 540 °C to obtain an MFI-type heteroatom molecular sieve containing framework cerium element; S3. Use the MFI-type heteroatom molecular sieve as a carrier to anchor metallic palladium, and obtain a palladium / cerium-doped pure silica molecular sieve or a palladium / cerium-doped silica-alumina molecular sieve catalytic material through calcination treatment; S4. Conduct an organic base treatment on the palladium / cerium-doped pure silica molecular sieve or the palladium / cerium-doped silica-alumina molecular sieve catalytic material, and after centrifugal drying and calcination, obtain a hollow palladium / cerium-doped pure silica molecular sieve or a hollow palladium / cerium-doped silica-alumina molecular sieve catalytic material with a hollow structure.

[0013] Preferably, the cerium source is one or more of cerium chloride, cerium nitrate, and cerium acetylacetonate, the silicon source is one or more of water glass, sodium silicate, methyl orthosilicate, tetraethyl orthosilicate, or silica sol, the organic template agent is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, and tetraethylammonium bromide, the aluminum source is one or more of aluminum chloride, aluminum sulfate, and sodium metaaluminate, the ligand is one or more of ethylenediamine, cetyltrimethylammonium bromide, ethylenediaminetetraacetic acid, acetylacetone, and sodium ethylenediaminetetraacetate, the source of the anchored metallic palladium is one or more of palladium nitrate and palladium chloride, and the organic base is one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and n-butylamine.

[0014] Preferably, the atomic ratio between the noble metal and the rare earth element is 0.06-0.60, and the molar ratio between the rare earth element and the organic ligand is 1:1-1:5; in step S1, the stirring time of the first mixed solution is 3-10 hours, and the stirring temperature is 30-40 °C. In step S1, the stirring time of the second mixed solution is 5-30 minutes, and the stirring temperature is 30-40 °C; In step S1, the cerium source used is replaced with a rare earth element source, and the rare earth element is selected from one or more of cerium and lanthanum; In step S3, the anchored metallic palladium is replaced with a noble metal, and the noble metal is selected from one or more of palladium and platinum.

[0015] Preferably, 6. When the rare earth element is lanthanum, the lanthanum source is one or more of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate; When the noble metal is platinum, the platinum source is one or more of chloroplatinic acid, tetraammineplatinum nitrate, and platinum sulfate; In step S2, the crystallization temperature is 120-180 °C, and the crystallization time is 72-120 hours; In step S4, the temperature of the organic base treatment is 80-170 °C, and the treatment time is 72-120 hours; In the composite catalytic material, the mass percentage of cerium is 0.5% - 5%, and the mass percentage of palladium is 0.05% - 0.4%.

[0016] Preferably, in the step S, a mixing device is used for preparation. The mixing device includes a reaction kettle, a feeding mechanism, a motor, a main shaft, a main stirring rod, and a reaction assembly; the reaction kettle is connected to the feeding mechanism, the upper part of the reaction kettle is rotationally connected to the main shaft, the main stirring rod is connected to the main shaft, and the reaction assembly is arranged inside the reaction kettle; The reaction assembly includes a tank body, a feeding pipe, a secondary stirring rod, an inner cylinder, a liquid outlet, an outer cylinder, an annular pipe, and a plurality of dropping heads; The tank body is connected to the inner wall of the reaction kettle, the upper part of the tank body is rotationally connected to the secondary stirring rod, the feeding pipe passes through the reaction kettle and is connected to the upper part of the tank body, the inner cylinder is connected to the lower part of the tank body, the outer cylinder is arranged outside the inner cylinder, the outer cylinder is connected to the bottom of the tank body, the liquid outlet is processed on the inner cylinder, the outer cylinder is connected to the annular pipe, and the plurality of dropping heads are connected to the annular pipe.

[0017] Preferably, a linkage mechanism is further included; the linkage mechanism includes a first gear, a first gear ring, a limiting plate, a bottom plate, a back plate, a spring, a pawl, and a ratchet; The first gear is meshed and connected with the first gear ring, the first gear ring is rotationally connected to the limiting plate, the limiting plate is connected to the inner wall of the reaction kettle, the first gear ring is connected to the main shaft, the first gear is connected to the bottom plate, the bottom plate is connected to the back plate, the back plate is connected to the pawl through the spring, the pawl is rotationally connected to the back plate, the pawl is clamped with the ratchet, and the ratchet is connected to the secondary stirring rod.

[0018] Preferably, a driving mechanism and a material control mechanism are further included, and the driving mechanism is arranged between the first gear and the bottom plate; The driving mechanism includes a connecting shaft, a second gear ring, a third gear ring, a bracket, an inner ring, a rotating plate, a stop bar, a shaft body, a torsion spring, a lever, and a mounting bracket; The connecting shaft is rotatably connected to the mounting frame, the mounting frame is connected to the reaction kettle, the connecting shaft is connected to the second gear ring, the second gear ring is connected to the third gear ring, the third gear ring is rotatably connected to the bracket, the bracket is connected to the reaction kettle, the inner side of the third gear ring is connected to the inner ring, the rotating plate is connected to the shaft body, the shaft body is rotatably connected to the inner ring, the torsion spring is sleeved on the shaft body, and the two ends of the torsion spring are respectively connected to the bottom of the inner ring and the lower part of the shaft body. The side surface of the rotating plate is attached to the stop bar, the stop bar is connected to the inner ring, and the stop bar limits the rotating plate to rotate in only one direction. The rotating plate corresponds to the lever, and the lever is connected to the bottom plate; The material control mechanism includes a convex block, a rod body, a reciprocating groove, a clamping block, two limiting rods, a connecting rod and a cylinder; The convex block is connected to the mounting frame, the convex block is rotatably connected to the rod body, the rod body is connected to the connecting shaft, the reciprocating groove is machined on the rod body, the clamping block is slidably connected to the reciprocating groove, the clamping block is slidably connected to the two limiting rods, the two limiting rods are connected to the convex block, the clamping block is connected to the cylinder through the connecting rod, and the cylinder is arranged between the inner cylinder and the outer cylinder, and the inner wall and the outer wall of the cylinder are respectively attached to the inner cylinder and the outer cylinder.

[0019] In the third aspect of the present invention, an application of an MFI-type heteroatom molecular sieve metal-coated composite catalytic material is provided.

[0020] Before the reaction, the composite catalytic material is activated in a helium atmosphere for 1 to 3 hours, and then methane and air are introduced for catalytic oxidation reaction, and the gas hourly space velocity is 30,000 to 120,000 h -1 .

[0021] One or more technical solutions provided in the present application have at least the following technical effects or advantages: 1. An MFI-type heteroatom molecular sieve metal-coated composite catalytic material, a preparation method and an application provided by the present invention. The hollow structure can realize the confinement effect on two metals in the physical space. At the same time, the heteroatoms in the molecular sieve can have a strong interaction with the coated metal, resulting in electron transfer and changing the adsorption and desorption of intermediate species. The framework heteroatoms and the coated metal can play a synergistic catalytic role, effectively improving the catalytic activity of the bimetallic catalytic material. This preparation method solves the problem that the existing rare earth element has a large atomic radius and is difficult to enter the framework. At the same time, the metal atoms in the framework can interact with the coated noble metal, improving its dispersion, realizing the reduction of noble metal, and at the same time improving its high-temperature thermal stability. Moreover, the MFI-type heteroatom hollow coating structure can stabilize the noble metal at high temperature and shows good reaction effects in methane catalytic oxidation.

[0022] It should be understood that the content described in the summary of the invention is not intended to limit the key or important features of the embodiments of the present invention, nor to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In conjunction with the accompanying drawings and with reference to the following detailed description, the above and other features, advantages, and aspects of the embodiments of the present invention will become more apparent. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein: Figure 1 FIG. shows a transmission electron microscope image of Example 1 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 2 FIG. shows an XRD pattern of Example 4 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 3 FIG. shows a transmission electron microscope image of Example 4 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 4 FIG. shows a comparison chart of the methane conversion rates of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 5 FIG. shows a comparison chart of the methane conversion rates of the catalysts prepared in Example 1 and Example 5 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 6 FIG. shows an XRD pattern of Example 5 of the method for preparing an MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to the present invention; Figure 7 FIG. shows a three-dimensional connection structure schematic diagram of a mixing device according to an embodiment of the present invention; Figure 8 FIG. shows an exploded view of a mixing device according to an embodiment of the present invention; Figure 9 FIG. shows a connection structure schematic diagram of the motor, main stirring rod, and main shaft of a mixing device according to an embodiment of the present invention; Figure 10 FIG. shows a connection structure schematic diagram of the reaction component and the driving mechanism of a mixing device according to an embodiment of the present invention; Figure 11 FIG. shows an exploded view of the reaction component of a mixing device according to an embodiment of the present invention; Figure 12 FIG. shows an exploded view of the driving component of a mixing device according to an embodiment of the present invention; Figure 13 The schematic diagram of the connection structure of the annular tube and the dropping head of the mixing device according to an embodiment of the present invention is shown; Figure 14 The schematic diagram of the connection structure of the material control mechanism of the mixing device according to an embodiment of the present invention is shown; Figure 15 The partial enlarged view of the driving mechanism of the mixing device according to an embodiment of the present invention is shown.

[0024] The reference numerals are as follows: 1 - reaction kettle, 2 - motor, 3 - feeding mechanism, 4 - reaction assembly, 401 - tank body, 402 - secondary stirring rod, 403 - feed pipe, 404 - inner cylinder, 405 - liquid outlet, 406 - outer cylinder, 407 - annular tube, 408 - dropping head, 5 - driving mechanism, 501 - connecting shaft, 502 - second gear ring, 503 - third gear ring, 504 - bracket, 505 - inner ring, 506 - rotating plate, 507 - stop bar, 508 - shaft body, 509 - torsion spring, 510 - lever, 511 - mounting bracket, 6 - material control mechanism, 601 - convex block, 602 - rod body, 603 - reciprocating groove, 604 - clamping block, 605 - limiting rod, 606 - connecting rod, 607 - cylinder body, 7 - linkage mechanism, 701 - first gear, 702 - first gear ring, 703 - limiting plate, 704 - bottom plate, 705 - back plate, 706 - spring, 707 - pawl, 708 - ratchet, 8 - main stirring rod, 9 - main shaft. Detailed implementation manners

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] In addition, the term "and / or" in this article is only a relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0027] An MFI - type heteroatom molecular sieve metal - coated composite catalytic material, and the composite catalytic material includes the following components: The MFI - type molecular sieve, as a basic carrier, has a specific topological structure; Rare earth elements, heteroatoms doped in the molecular sieve framework, selected from one or more of cerium and lanthanum; Noble metals, supported on the molecular sieve, selected from one or more of palladium and platinum; Among them, the ratio of each component is as follows: Calculated by the total mass percentage of the catalyst, the content of the rare earth element is 0.5% - 5%; Calculated by the total mass percentage of the catalyst, the content of the noble metal is 0.05% - 0.4%; The atomic ratio of the noble metal to the rare earth element is 0.06 - 0.60; The molar ratio of the rare earth element to the organic ligand is 1:1 - 1:5.

[0028] Among them, the MFI-type molecular sieve is a pure silica molecular sieve or a silica-alumina molecular sieve; the composite catalytic material has a hollow structure and is formed by treatment with an organic base.

[0029] As Figures 1 to 6 shown, in addition, another embodiment of the present invention also provides a preparation method of an MFI-type heteroatom molecular sieve metal-coated composite catalytic material.

[0030] Example 1: S1: The preparation process of the catalyst is as follows: Take 31.6270 g of tetrapropylammonium hydroxide aqueous solution (25 wt.%) and add 30.0 g of tetraethyl orthosilicate, stir in a 35-degree water bath for 3 hours until the tetraethyl orthosilicate is completely hydrolyzed, marked as the first mixed solution (designated as solution A); Dissolve 0.1628 g of cerium chloride heptahydrate in 72.1850 g of water, stir in a 35-degree water bath for 5 minutes, marked as the second mixed solution (designated as solution B); Slowly drop solution B into solution A, and continue to stir in a 35-degree water bath for 2 hours; S2: After removing alcohol, it is loaded into a autoclave reactor and crystallized at 170 degrees for 72 hours. After cooling, it is washed to neutral, dried in an 80-degree oven, and finally transferred to a muffle furnace and calcined at 540 degrees to prepare a framework heteroatom Ce@S-1 molecular sieve catalyst; S3: Take 0.0377 g of palladium nitrate dihydrate and dissolve it in 1.5048 g of water, stir while dropping until completely dissolved, and gradually add it to the Ce@S-1 support, transfer it to an 80-degree oven for drying, and finally calcine it in a 500-degree muffle furnace to obtain a heteroatom molecular sieve-supported palladium-based catalyst, recorded as Pd / Ce@S-1; S4: Add 60 g of aqueous tetrapropylammonium hydroxide solution (0.3 molar concentration) to the Pd / Ce@S-1 molecular sieve catalyst, stir in a 35 °C water bath for 0.5 hours, transfer to a crystallization kettle and crystallize at 170 °C for 72 hours. After cooling, wash until neutral, dry in an 80 °C oven, and finally calcine in a muffle furnace at 540 °C to obtain the Pd / Ce@S-1-H molecular sieve catalyst with a hollow structure. The transmission electron microscope results are shown in the accompanying drawings of the specification Figure 1 。

[0031] Example 2: S1: Stir in a 40 °C water bath for 10 hours when preparing solution A, and repeat the operation steps in S1 of Example 1 for other steps of solution A. Dissolve 0.1628 g of cerium chloride heptahydrate and 0.0377 g of palladium nitrate dihydrate in 72.185 g of water, stir in a 30 °C water bath for 23 minutes, and label it as solution B; slowly drop solution B into solution A, stir in a 35 °C water bath for 12 hours, and repeat the remaining operation steps of Example 1; S2: After removing alcohol, then load it into a kettle reactor and crystallize at 120 °C for 120 hours. Cool and wash until neutral to obtain the Pd-Ce@S-1 catalyst, and repeat the remaining operation steps of Example 1; S3, S4: Transfer to a crystallization kettle and crystallize at 80 °C for 100 hours. Repeat the steps of S3 and S4 in Example 1 for other steps to obtain the heteroatom-confined Pd-Ce@S-1-H molecular sieve catalyst with a hollow structure.

[0032] Example 3: S1: Stir in a 30 °C water bath for 5 hours when preparing solution A, and repeat the operation steps in S1 of Example 1 for other steps of solution A. Add 72.185 g of water to solution A and label it as solution B; slowly drop solution B into solution A, stir in a 35 °C water bath for 24 hours, and repeat the remaining operation steps of Example 1; S2: After removing alcohol, then load it into a crystallization kettle and crystallize at 180 °C for 72 hours. Cool, wash, dry in an 80 °C oven, and finally calcine in a muffle furnace at 540 °C to obtain the S-1 pure silica molecular sieve catalyst, and repeat the remaining operation steps of Example 1; S3: Dissolve 0.1628 g of cerium chloride heptahydrate in 1.4548 g of water, stir while dropping until completely dissolved, then gradually and evenly drop it onto the S-1 support, dry in an 80 °C oven, and finally calcine in a muffle furnace at 400 °C to obtain the Ce / S-1 molecular sieve catalyst; dissolve 0.0377 g of palladium nitrate dihydrate in 1.5048 g of water, stir while dropping until uniform, gradually add it to the Ce / S-1 support, dry in an 80 °C oven, and finally calcine in a muffle furnace at 500 °C to obtain the Pd / Ce / S-1 molecular sieve catalyst, and repeat the remaining operation steps of Example 1; S4: Transfer to a crystallization kettle and crystallize at 110 °C for 120 hours. Repeat the operation steps in S4 of Example 1 for other steps to obtain the Pd / Ce / S-1-H molecular sieve catalyst.

[0033] Example 4: S1: The preparation method of solution B is as follows: First, dissolve 0.1628 g of cerium chloride heptahydrate in 0.0525 g of ethylenediamine, then add 72.185 g of water, and stir in a water bath at 40 °C for 30 minutes. Repeat the remaining operation steps of Example 1.

[0034] S2, S3 and S4: The same as steps S2, S3 and S4 in Example 1, and the Pd / Ce@S-1-EDA-H molecular sieve catalyst can be obtained. The XRD characterization results are shown in the accompanying drawings of the specification. Figure 2 。

[0035] Example 5: S1: Take 65.7200 g of tetrapropylammonium hydroxide aqueous solution (25 wt.%) and add 62.3300 g of tetraethyl orthosilicate and 112.3000 g of water, stir in a water bath at 40 °C for 3 hours until the tetraethyl orthosilicate is completely hydrolyzed, and label it as solution A; dissolve 0.9971 g of aluminum sulfate octadecahydrate in 37.6700 g of water, and label it as solution B; slowly add solution B to solution A, and continue to stir in a water bath at 35 °C for 2 hours. Repeat the remaining operation steps of Example 1.

[0036] S2: Dissolve 0.9742 g of cerium chloride heptahydrate in 5.7255 g of water, load it into a autoclave reactor and crystallize at 160 °C for 82 hours. After cooling, wash it to neutral, dry it in an oven at 80 °C, and finally transfer it to a muffle furnace and calcine it at 540 °C to prepare the framework heteroatom Ce@ZSM-5 molecular sieve catalyst. Repeat the remaining operation steps of Example 1.

[0037] S3, S4: The same as steps S3, S4 in Example 1, and the Pd / Ce@ZSM-5--H molecular sieve catalyst is obtained.

[0038] Example 6: S1: The preparation method of solution B is as follows: Dissolve 0.1628 g of cerium chloride heptahydrate (molar amount 0.000437 mol) in 0.0263 g of ethylenediamine (molar amount 0.000437 mol), and then add 72.185 g of water. The remaining operation steps are the same as those in Example 1.

[0039] S2: After removing alcohol, load it into a autoclave reactor and crystallize at 170 °C for 72 hours. After cooling, wash it to neutral, dry it in an oven at 80 °C, and finally calcine it in a muffle furnace at 540 °C to prepare the framework heteroatom Ce@S-1 molecular sieve catalyst.

[0040] S3 and S4: The same steps as in Example 1 were performed to obtain the Pd / Ce@S-1-H molecular sieve catalyst.

[0041] Example 7: S1: 0.0401 g (mass fraction 0.5%) of cerium chloride heptahydrate was dissolved in 72.185 g of water, and the remaining operation steps were repeated as in Example 1.

[0042] S2 and S3: The same as steps S2 and S3 in Example 1.

[0043] S4: The same as step S4 in Example 1, and finally the Pd / La@S-1-H molecular sieve catalyst was obtained.

[0044] Example 8: S1: The method for preparing solution B was as follows: 0.0806 g (mass fraction 1%) of cerium chloride heptahydrate was dissolved in 72.185 g of water, and the remaining operation steps were repeated as in Example 1.

[0045] S2, S3, and S4: The remaining operation steps were repeated as in S2, S3, and S4 in Example 1 to obtain the Pd / Ce@S-1-H molecular sieve catalyst.

[0046] Example 9: S1: The method for preparing solution B was as follows: 0.1628 g of cerium chloride heptahydrate was dissolved in 0.1313 g of ethylenediamine, and then 72.185 g of water was added; the remaining operation steps were repeated as in Example 1.

[0047] S2, S3, and S4: The remaining operation steps were repeated as in S2, S3, and S4 in Example 1 to obtain the Pd / Ce@S-1-EDA-H molecular sieve catalyst.

[0048] Example 10: S1: The method for preparing solution B was as follows: 0.4199 g (mass fraction 5%) of cerium chloride heptahydrate was dissolved in 72.185 g of water, and the remaining operation steps were repeated as in Example 1.

[0049] S2, S3, and S4: The remaining operation steps were repeated as in S2, S3, and S4 in Example 1 to obtain the Pd / Ce@S-1-H molecular sieve catalyst.

[0050] It should be added that in step S1, whether to add an aluminum source is selected according to the required molecular sieve type. When the aluminum source is not added, a gel for palladium / cerium-doped pure silicon molecular sieve is prepared (such as Pd / Ce@S-1, see Example 1); when the aluminum source is added, a gel for palladium / cerium-doped silicon-aluminum molecular sieve is prepared (such as Pd / Ce@ZSM-5, see Example 5). When the aluminum source is added in step S1, the molar ratio of the aluminum source to the silicon source is 0.01-0.1. The whole preparation process adopts the method of hydrothermal treatment followed by alkali treatment. Among them, the cerium source is one or more of cerium chloride, cerium nitrate, and cerium acetylacetonate; the silicon source is one or more of water glass, sodium silicate, methyl orthosilicate, tetraethyl orthosilicate, or silica sol; the organic template agent is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, and tetraethylammonium bromide; the aluminum source is one or more of aluminum chloride, aluminum sulfate, and sodium metaaluminate; the ligand is one or more of ethylenediamine, cetyltrimethylammonium bromide, ethylenediaminetetraacetic acid, acetylacetone, and sodium ethylenediaminetetraacetate; the source of the anchored metal palladium is one or more of palladium nitrate and palladium chloride; the organic base is one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and n-butylamine. The atomic ratio between the noble metal and the rare earth element is 0.06-0.60. Optionally, fixing cerium (0.000437 mol): 0.00698 g of palladium is required (about 0.00002622 mol), and the atomic ratio at this time is 0.06. Fixing palladium (0.000141 mol): 0.8756 g of cerium is required (about 0.00235 mol), and the atomic ratio at this time is 0.6. In the example, the noble metal (palladium): 0.0377 g of palladium nitrate dihydrate is used, with a molecular weight of 266.46 g / mol and a molar amount of 0.0377÷266.46≈0.000141 mol. Rare earth element (cerium): 0.1628 g of cerium chloride heptahydrate is used, with a molecular weight of 372.58 g / mol and a molar amount of 0.1628÷372.58≈0.000437 mol. Atomic ratio: 0.000141÷0.000437≈0.323. The molar ratio between the rare earth element and the organic ligand is 1:1-1:5. In step S1, the stirring time of the first mixed solution is 3-10 hours, and the stirring temperature is 30-40 °C. In step S1, the stirring time of the second mixed solution is 5-30 minutes, and the stirring temperature is 30-40 °C; in step S1, the cerium source used is replaced with a rare earth element source, and the rare earth element is selected from one or more of cerium and lanthanum.In step S3, the anchored palladium metal is replaced with a noble metal selected from one or more of palladium and platinum; when the rare earth element is lanthanum, the lanthanum source is one or more of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate; when the noble metal is platinum, the platinum source is one or more of chloroplatinic acid, tetraammineplatinum nitrate, and platinum sulfate; in step S2, the crystallization temperature is 120 - 180 degrees and the crystallization time is 72 - 120 hours; in step S4, the temperature for organic base treatment is 80 - 170 degrees and the treatment time is 72 - 120 hours; in the composite catalyst material, the mass percentage of cerium content is 0.5% - 5%, and the mass percentage of palladium content is 0.05% - 0.4%. Throughout the range of the molar ratio of rare earth element to organic ligand from 1:1 to 1:5, the catalyst can effectively catalyze the methane oxidation reaction. When the molar ratio is 1:2, the T. 50 value can reach 322 degrees, showing the best performance, while other molar ratios also have good effects. Throughout the range of cerium content from 0.5% to 5%, the catalyst can effectively catalyze the methane oxidation reaction. When the content is 2%, the T 50 value can reach 341 degrees, showing the best performance, while other contents also have good effects. For rare earth elements cerium or lanthanum, the catalyst can effectively catalyze the methane oxidation reaction. When the rare earth element is cerium, it is optimal, and the T 50 value can reach 341 degrees, showing the best performance, while the rare earth element lanthanum also has good effects. Throughout the range of crystallization time from 24 to 120 hours, the catalyst can effectively catalyze the methane oxidation reaction. When it is 72 hours, it is optimal, and the T 50 value can reach 341 degrees, showing the best performance, while 24 hours and 120 hours also have good effects. Among them, the atomic ratio between the noble metal and the rare earth element is 0.06 - 0.60.

[0051] Among them, "Pd / Ce@S-1" is "palladium / cerium-doped pure silica molecular sieve", which means palladium is loaded on a pure silica MFI molecular sieve with a cerium-containing framework.

[0052] "Pd / Ce@ZSM-5" is "palladium / cerium-doped aluminosilicate molecular sieve", which means palladium is loaded on an aluminum-containing MFI molecular sieve with a cerium-containing framework.

[0053] "Pd / Ce@S-1-H" is "hollow palladium / cerium-doped pure silica molecular sieve", emphasizing the formation of a hollow structure through alkali treatment.

[0054] "Pd / Ce@ZSM-5-H" is "hollow palladium / cerium-doped aluminosilicate molecular sieve", the same as above, applicable to aluminum-containing molecular sieves.

[0055] Comparative Example 1: S1: When preparing Solution A, stir in a water bath at 30 °C for 5 hours, and repeat the operation steps in S1 of Example 1 for other steps of Solution A. Add 72.185 g of water to Solution A and label it as Solution B; slowly drip Solution B into Solution A, stir in a water bath at 35 °C for 24 hours, and repeat the remaining operation steps of Example 1; S2: After removing alcohol, then load it into a crystallization kettle and crystallize at 180 °C for 72 hours. Wash after cooling, dry in an oven at 80 °C, and finally calcine in a muffle furnace at 540 °C to obtain the S-1 pure silica molecular sieve catalyst, and repeat the remaining operation steps of Example 1; S3: Dissolve 0.1628 g of cerium chloride heptahydrate in 1.4548 g of water, stir while dripping until completely dissolved, then gradually and evenly drip it onto the S-1 support, and dry in an oven at 80 °C, and finally calcine in a muffle furnace at 400 °C to obtain the Ce / S-1 molecular sieve catalyst; dissolve 0.0377 g of palladium nitrate dihydrate in 1.5048 g of water, stir while dripping until uniform, gradually add it to the Ce / S-1 support, and dry in an oven at 80 °C, and finally calcine in a muffle furnace at 500 °C to obtain the Pd / Ce / S-1 molecular sieve catalyst, and repeat the remaining operation steps of Example 1; S4: Transfer to a crystallization kettle and crystallize at 110 °C for 120 hours, and repeat the operation steps in S4 of Example 1 for other steps to obtain the Pd / Ce / S-1-H molecular sieve catalyst.

[0056] Comparative Example 2 (2Ce / S-1_S) The preparation process of the REF-1 catalyst is as follows: S1: Repeat the operation steps in Comparative Example S2; S2: Dissolve 0.1628 g of cerium chloride in 1.4548 g of water, and gradually add it dropwise to S-1; dry in an oven at 80 °C, and finally calcine in a muffle furnace at 400 °C to obtain the 2Ce / S-1-S catalyst.

[0057] Comparative Example 3 (0.2Pd / S-1_S) The preparation process of the REF-2 catalyst is as follows: S1: Repeat the operation steps in Comparative Example S2; S2: Dissolve 0.015 g of palladium nitrate dihydrate in 1.0099 g of water, and gradually add it dropwise to S-1; place it in an oven at 80 °C to dry, and finally calcine in a muffle furnace at 500 °C to obtain the 0.2Pd / S-1-S molecular sieve catalyst.

[0058] Comparative Example 4 (0.2Pd@S-1_H) The preparation process of the REF-3 catalyst is as follows: S1: Repeat the operation steps in S1 of Example 1 for Solution A; S2: Prepare a Pd salt solution by dissolving 0.015 g of palladium nitrate dihydrate in 72.1850 g of water, marked as Solution B. Slowly add Solution B dropwise to Solution A and continue stirring at 35 °C for 2 hours. After removing the alcohol, transfer it to a autoclave reactor and crystallize at 170 °C for 72 hours. After cooling, wash it until neutral, dry it in an oven at 80 °C, and finally transfer it to a muffle furnace and calcine at 540 °C to prepare the coated Pd@S-1 catalyst; S3: Add 60 g of tetrapropylammonium hydroxide solution (0.3 M) to the Pd@S-1 zeolite catalyst, stir it in a water bath at 35 °C for 0.5 hours, and then crystallize it at 170 °C for 72 hours; after cooling and washing, dry it at 80 °C and calcine it at 540 °C to obtain the Pd@S-1-H zeolite catalyst; Comparative Example 5 (0.2Pd / Ce / S-1_S) The preparation process of the REF-4 catalyst is as follows: S1: Repeat the operation steps in S1 and S2 of Comparative Example 2; S2: Dissolve 0.015 g of palladium nitrate dihydrate in 1.0099 g of water, and add it dropwise to Ce / S-1-S; place it in an oven at 80 °C to dry, and finally calcine it in a muffle furnace at 500 °C to obtain Pd / Ce / S-1-S.

[0059] As Figures 7 to 15As shown in the figure, the mixing device includes a reaction kettle 1, a feeding mechanism 3, a motor 2, a main shaft 9, a main stirring rod 8, and a reaction assembly 4. The reaction kettle 1 is a closed container for containing reaction materials, and a feeding port is provided at its top. The feeding mechanism 3 is hermetically connected to the feeding port through a pipeline for quantitatively transporting reaction raw materials into the reaction kettle 1. The motor 2 is fixedly installed at the top of the reaction kettle 1, and the output end of the motor 2 is connected to the main shaft 9. The main shaft 9 is rotationally connected to the top of the reaction kettle 1 through a bearing, and the main shaft 9 extends axially into the reaction kettle 1 along the axis of the reaction kettle 1. The main stirring rod 8 is fixedly connected to the lower end of the main shaft 9 and rotates synchronously with the main shaft 9 for stirring the materials in the reaction kettle 1. The reaction assembly 4 is arranged inside the reaction kettle 1 for further optimizing the reaction process. Among them, the outer walls of the tank body 401 and the reaction kettle 1 are both designed as double-layer structures, and a circulating water bath is passed through the middle to form a stable heating environment. The reaction assembly 4 includes a tank body 401, a feeding pipe 403, a secondary stirring rod 402, an inner cylinder 404, a liquid outlet 405, an outer cylinder 406, an annular pipe 407, and a plurality of dropping heads 408. The tank body 401 is a cylindrical structure, and the outer wall of the tank body 401 is fixed to the inner wall of the reaction kettle 1 by welding or bolts. The inside of the tank body 401 is used for the reaction of other materials. The secondary stirring rod 402 is rotationally connected to the top of the tank body 401 through a bearing. The axis of the secondary stirring rod 402 is parallel to the axis of the main shaft 9, and stirring blades are provided on the secondary stirring rod 402 for stirring the materials in the tank body 401. One end of the feeding pipe 403 passes through the top of the reaction kettle 1 and is hermetically connected to the top of the tank body 401, and the other end of the feeding pipe 403 is communicated with an external raw material supply device for transporting specific reaction materials into the tank body 401. The bottom of the tank body 401 is fixedly connected with an inner cylinder 404. The inner cylinder 404 is a hollow cylindrical structure, and an outer cylinder 406 is coaxially sleeved outside it. The top of the outer cylinder 406 is fixed to the bottom of the tank body 401 by welding or bolts, and an annular gap is formed between the outer cylinder 406 and the inner cylinder 404 for guiding the liquid material. A plurality of liquid outlets 405 are machined on the side wall of the inner cylinder 404, and the liquid outlets 405 are evenly distributed along the circumferential direction of the inner cylinder 404 for releasing the liquid material in the inner cylinder 404 into the annular gap between the outer cylinder 406 and the inner cylinder 404 in a controlled manner. The bottom of the outer cylinder 406 is connected with an annular pipe 407 through a pipeline. The annular pipe 407 is a closed annular pipeline arranged along the circumferential direction of the bottom of the outer cylinder 406. A plurality of dropping heads 408 are communicated with the lower surface of the annular pipe 407, and the plurality of dropping heads 408 are evenly distributed along the circumferential direction of the annular pipe 407. Each dropping head 408 is a nozzle structure for evenly releasing the liquid material in the form of drops into the bottom area of the reaction kettle 1, so as to achieve precise dropping and dispersion of the materials.

[0060] In actual use, the feeding mechanism 3 conveys the initial reaction materials into the reaction kettle 1 through the feeding port of the reaction kettle 1. The motor 2 drives the main shaft 9 to rotate, and the motor 2 is a servo motor capable of controlling forward and reverse rotation. The main shaft 9 drives the main stirring rod 8 to initially mix and stir the materials in the reaction kettle 1. At the same time, specific reaction materials enter the tank body 401 through the feeding pipe 403, and the auxiliary stirring rod 402 rotates in the tank body 401 to stir the materials to ensure uniformity. The materials in the tank body 401 flow out through the liquid outlet 405 of the inner cylinder 404, enter the annular gap between the inner cylinder 404 and the outer cylinder 406, and then are distributed to a plurality of dropping heads 408 through the annular pipe 407 at the bottom of the outer cylinder 406. The dropping heads 408 uniformly release the materials in a dropwise form to the bottom area of the reaction kettle 1, and are further mixed with the materials stirred by the main stirring rod 8, thereby realizing an efficient and uniform reaction process. By setting the reaction assembly 4 and combining the dual stirring mechanisms of the main stirring rod 8 and the auxiliary stirring rod 402, the uniformity of material mixing is improved; the collaborative design of the inner cylinder 404, the outer cylinder 406, the annular pipe 407, and the dropping heads 408 realizes the precise dropping and dispersion of the liquid materials, avoiding the problem of uneven material distribution in traditional reaction equipment.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art can make various changes and modifications to the above embodiments without departing from the spirit and scope of the present invention. For example, the number of the dropping heads 408 or the aperture of the liquid outlet 405 can be adjusted to meet different reaction requirements. Therefore, all equivalent technical solutions belong to the protection scope of the present invention.

[0062] In this embodiment, a linkage mechanism 7 is further included. The linkage mechanism 7 is disposed inside the reaction kettle 1 and is used to achieve power transmission and coordinated movement between the main shaft 9 and the auxiliary stirring rod 402 so as to optimize the stirring effect. The linkage mechanism 7 includes a first gear 701, a first toothed ring 702, a limiting plate 703, a bottom plate 704, a back plate 705, a spring 706, a pawl 707 and a ratchet 708. The first toothed ring 702 is an annular gear, and its inner side is connected to the outer periphery of the main shaft 9 by key connection or bolt fixation and rotates synchronously with the main shaft 9. The limiting plate 703 is a circular plate-like structure. The limiting plate 703 is fixedly connected to the inner wall of the reaction kettle 1, for example, by bolts or welding. A through groove is provided at the center of the limiting plate 703, and the first toothed ring 702 is rotatably connected to the through groove through a plurality of balls to ensure the stability of the first toothed ring 702 during rotation. It is also possible to ensure the normal rotation of the first toothed ring 702 by setting bearings on the inner side of the limiting plate 703. The first gear 701 is meshed with the internal teeth of the first toothed ring 702, and the center of the first gear 701 is fixedly connected to the rotating shaft of the bottom plate 704 by key connection. The bottom plate 704 is a flat plate structure. One end of the bottom plate 704 is connected to the back plate 705. The back plate 705 is a vertically arranged plate-like member for supporting subsequent components. The side surface of the back plate 705 is elastically connected to the pawl 707 through the spring 706. One end of the spring 706 is fixed to the back plate 705, and the other end is connected to the middle part of the pawl 707 to provide an elastic restoring force for the pawl 707. One end of the pawl 707 is rotatably connected to the back plate 705 by hinge, so that the pawl 707 can swing within a certain angle range. The free end of the pawl 707 is engaged with the tooth groove of the ratchet 708 to form a one-way transmission structure. The ratchet 708 is fixedly connected to the upper end of the auxiliary stirring rod 402 by key connection, and the auxiliary stirring rod 402 is rotatably connected to the top of the tank body 401 through a bearing (as described above). Each component of the above-mentioned linkage mechanism 7 works together to ensure that the rotation of the main shaft 9 can drive the auxiliary stirring rod 402 to rotate in a controllable manner.

[0063] In actual use, after the reaction device is started, the motor 2 drives the main shaft 9 to rotate. The main shaft 9 drives the main stirring rod 8 to stir the materials in the reaction kettle 1. At the same time, the main shaft 9 drives the first gear ring 702 to rotate synchronously through a key connection. The rotation of the first gear ring 702 drives the first gear 701 to rotate through a meshing relationship. The rotational force of the first gear 701 is transmitted to the back plate 705 through the bottom plate 704. Through the combined action of hinge and spring 706, the free end of the pawl 707 is pushed to keep engaged with the tooth groove of the ratchet 708, thereby driving the ratchet 708 to rotate. The rotation of the ratchet 708 further drives the auxiliary stirring rod 402 to rotate in the tank body 401, locally stirring the materials in the tank body 401. Due to the one-way engagement design of the pawl 707 and the ratchet 708, the auxiliary stirring rod 402 only moves with the rotation of the main shaft 9 in a specific direction. In the reverse or non-driven state, the ratchet 708 can remain stationary to avoid unnecessary power interference. Through the setting of the linkage mechanism 7, an efficient power transmission mechanism is formed between the main shaft 9 and the auxiliary stirring rod 402. The rotation speed and direction of the auxiliary stirring rod 402 can be adjusted through the tooth ratio of the first gear 701 and the first gear ring 702 and the one-way design of the pawl 707 and the ratchet 708, so as to adapt to different reaction requirements. In reactions that require intermittent stirring, the one-way transmission of the pawl 707 and the ratchet 708 can achieve the intermittent movement of the auxiliary stirring rod 402. The linkage mechanism 7 combines gear transmission and ratchet mechanism to achieve the coordinated movement of the main shaft 9 and the auxiliary stirring rod 402, which not only improves the overall efficiency of the stirring system, but also enhances the adaptability of the equipment to complex reaction processes. The elastic connection design of the spring 706 and the pawl 707 ensures the stability and reliability of the transmission and reduces mechanical wear. In addition, the structure of the linkage mechanism 7 is compact and is installed inside the reaction kettle 1 without increasing the overall volume of the equipment, which is convenient for industrial application.

[0064] In this embodiment, a driving mechanism 5 and a material control mechanism 6 are further included. The driving mechanism 5 is arranged between the first gear 701 and the bottom plate 704. The material control mechanism 6 is arranged between the inner cylinder 404 and the outer cylinder 406 of the reaction assembly 4, and is used to adjust the outflow of materials, so as to optimize the uniformity and controllability of the reaction process. The driving mechanism 5 includes a connecting shaft 501, a second gear ring 502, a third gear ring 503, a bracket 504, an inner ring 505, a rotating plate 506, a retaining bar 507, a shaft body 508, a torsion spring 509, a lever 510 and a mounting frame 511. The mounting frame 511 is fixed to the inner wall of the reaction kettle 1 by bolts or welding, and is used to support the components of the driving mechanism 5. The connecting shaft 501 is rotatably connected to the mounting frame 511 through a bearing, and one end of the connecting shaft 501 is fixedly connected to the second gear ring 502 by a key connection. The second gear ring 502 is an annular gear, and the external teeth of the second gear ring 502 are meshed and connected with the external teeth of the third gear ring 503. The third gear ring 503 is rotatably connected to the bracket 504 through a bearing. The bracket 504 is a frame structure and is fixed to the inner wall of the reaction kettle 1 to stabilize the rotation of the third gear ring 503. The inner side of the third gear ring 503 is fixedly connected with an inner ring 505 by bolts or welding. The inner ring 505 is a circular ring structure, and the inner wall thereof is rotatably connected with a shaft body 508 through a bearing. The shaft body 508 is a cylindrical structure, and the top of the shaft body 508 is fixedly connected with a rotating plate 506. The rotating plate 506 is a circular or sector-shaped plate member. A torsion spring 509 is sleeved on the outer periphery of the shaft body 508. One end of the torsion spring 509 is fixed to the bottom of the inner ring 505, and the other end is fixed below the shaft body 508. The torsion spring 509 provides an elastic restoring force for the rotating plate 506. A retaining bar 507 is fixed on the inner wall of the inner ring 505. The retaining bar 507 is an arc-shaped or strip-shaped protrusion, and the side surface thereof is attached to the side edge of the rotating plate 506, restricting the rotating plate 506 to rotate only in a single direction. The outer periphery of the rotating plate 506 corresponds to the position of the lever 510. The lever 510 is a rod-shaped structure, one end of which is fixed to the bottom plate 704, and the other end can swing under the push of the rotating plate 506, so as to drive the bottom plate 704 to move. The other end of the connecting shaft 501 is fixedly connected to the first gear 701 by a key connection to achieve power transmission. It should be noted that the lever 510 can drive the rotating plate 506 to rotate during the rotation of the bottom plate 704. That is to say, at this time, the rotating plate 506 is limited by the retaining bar 507. When the bottom plate 704 drives the lever 510 to rotate in this direction, the ratchet pawl 707 will not drive the ratchet wheel 708 to rotate at this time. Further, the rotation directions of the two are opposite. When the bottom plate 704 drives the lever 510 to rotate in the opposite direction, the ratchet pawl 707 will drive the ratchet wheel 708 to rotate, and the lever 510 will not drive the inner ring 505 to rotate through the rotating plate 506. At this time, the rotating plate 506 will rotate and drive the torsion spring 509 to deform.

[0065] The material control mechanism 6 includes a convex block 601, a rod body 602, a reciprocating groove 603, a clamping block 604, two limiting rods 605, a connecting rod 606, and a cylinder 607. The convex block 601 is a block structure and is fixed to the side of the mounting frame 511 by bolts. There is a hinge point on the convex block 601, and one end of the rod body 602 is rotatably connected to the convex block 601 through this hinge point. The other end of the rod body 602 is connected to the connecting shaft 501 by key connection or bolts and swings with the rotation of the connecting shaft 501. A reciprocating groove 603 is machined on the side of the rod body 602. The reciprocating groove 603 is a long-strip groove structure and extends along the length direction of the rod body 602. The clamping block 604 is a slider structure, and there is a protrusion on its back. This protrusion is embedded in the reciprocating groove 603, enabling the clamping block 604 to reciprocate along the reciprocating groove 603. There is a through hole on the side of the clamping block 604. The two limiting rods 605 are arranged in parallel and respectively pass through the through hole of the clamping block 604. The two ends of the limiting rods 605 are fixed to the convex block 601 and are used to limit the movement track of the clamping block 604 to ensure its stable sliding along the axial direction of the limiting rods 605. The bottom of the clamping block 604 is connected to the cylinder 607 through the connecting rod 606. The connecting rod 606 is a rigid rod, one end of which is hinged to the clamping block 604, and the other end is hinged to the top of the cylinder 607. The cylinder 607 is a hollow cylindrical structure and is arranged in the annular gap between the inner cylinder 404 and the outer cylinder 406. The inner wall of the cylinder 607 is in sliding fit with the outer wall of the inner cylinder 404, and the outer wall is in sliding fit with the inner wall of the outer cylinder 406. When the cylinder 607 moves upward along the axis, the liquid outlet 405 is no longer blocked by the cylinder 607, and the raw material in the tank body 401 flows into the outer cylinder 406 from the liquid outlet 405.

[0066] During actual use, after the reaction device is started, the motor 2 drives the main shaft 9 to rotate. The main shaft 9 transmits power to the connecting shaft 501 of the driving mechanism 5 through the first gear ring 702 and the first gear 701 of the linkage mechanism 7. When the bottom plate 704 rotates, it will drive the lever 510 to rotate. When the lever 510 rotates, it will touch the rotating plate 506. The rotating plate 506 (restricted by the blocking strip 507 and the torsion spring 509) drives the inner ring 505 to move synchronously during the rotation process. During the synchronous movement process of the inner ring 505, it drives the third gear ring 503 to rotate. When the third gear ring 503 rotates, it drives the second gear ring 502 to rotate. During the rotation process of the second gear ring 502, it drives the lower connecting shaft 501 and the rod body 602 to rotate.

[0067] At the same time, the rotation of the connecting shaft 501 drives the rod body 602 to swing around the hinge point of the protrusion 601, and the reciprocating groove 603 of the rod body 602 guides the clamping block 604 to slide back and forth along the limit rod 605. The sliding of the clamping block 604 drives the cylinder body 607 to move up and down axially in the annular gap between the inner cylinder 404 and the outer cylinder 406 through the connecting rod 606. The movement of the cylinder body 607 makes the liquid outlet 405 of the inner cylinder 404 covered or exposed in the annular gap, thereby realizing the lowering of the material. The released material is distributed to multiple drip heads 408 through the annular tube 407 at the bottom of the outer cylinder 406. The multiple drip heads 408 are evenly released to the bottom area of the reactor 1 in the form of drops, and further mixed with the material stirred by the main stirring rod 8. Through the setting of the driving mechanism 5, the power transmission of the linkage mechanism 7 is controlled, and the material control mechanism 6 is dynamically adjusted by the cylinder body 607. It is worth noting that the lever 510 can drive the rotating plate 506 to rotate as the bottom plate 704 rotates, that is, the rotating plate 506 is limited by the blocking bar 507 at this time, and when the bottom plate 704 drives the lever 510 to rotate in this direction, the ratchet 707 will not drive the ratchet wheel 708 to rotate. This is called the unloading process, and the driving mechanism 5 drives the cylinder 607 to close the multiple liquid outlets 405, and unloading is achieved in the process of opening the multiple liquid outlets 405. Furthermore, since the rotation directions of the two are opposite, when the bottom plate 704 drives the lever 510 to rotate in the opposite direction, the pawl 707 will drive the ratchet 708 to rotate, and the lever 510 will not drive the inner ring 505 to rotate through the rotating plate 506. At this time, the rotating plate 506 will rotate and drive the torsion spring 509 to deform (when the lever 510 touches the rotating plate 506 and rotates, the deformed torsion spring 509 is not enough to drive the third gear ring 503 to open by its own elastic force, which also achieves that the lower cylinder 607 will not block the multiple liquid outlets 405 during the mixing process, preventing the material from being lowered during the mixing process). This is called the mixing process. Through the forward and reverse switching of the motor 2, the device can flexibly switch between the feeding process and the mixing process. In the feeding process, the auxiliary stirring rod 402 is stationary, and the material is accurately released through the liquid outlet 405; in the mixing process, the liquid outlet 405 is closed, and the auxiliary stirring rod 402 stirs the material in the tank body 401 to ensure uniform batching. Through the ingenious design of the mechanical structure (such as the one-way linkage between the lever 510 and the rotating plate 506, the elastic limit of the torsion spring 509, and the dynamic adjustment of the cylinder 607), the equipment can realize the automatic switching between batching and unloading by relying only on the forward and reverse rotation of the motor 2, without the need for an additional electronic control system, which significantly reduces the equipment's dependence on complex electronic components, reduces manufacturing costs and maintenance difficulties, and improves the equipment's reliability in harsh environments.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it. Those skilled in the art can adjust the driving mechanism 5 and the material control mechanism 6 according to actual needs. For example, the tooth number ratio of the second gear ring 502 and the third gear ring 503 can be changed to optimize the transmission efficiency, or the length of the reciprocating groove 603 can be adjusted to change the moving stroke of the cylinder body 607. All equivalent technical solutions based on the concept of the present invention fall within the protection scope of the present invention.

[0069] In addition, another embodiment of the present invention also provides an application of an MFI type heteroatom molecular sieve metal-coated composite catalytic material, including: Performance test: The molecular sieve catalysts prepared in the above Examples 1-4 and Comparative Examples 1-4 were applied to the methane catalytic oxidation reaction to simulate the degradation effect of the hollow heteroatom molecular sieve-confined Pd-Ce metal system prepared by the present invention on VOCs.

[0070] Test method: The composite catalytic material was activated in a helium atmosphere for 1.5 hours, and programmed temperature methane oxidation was carried out in a continuous flow fixed bed reactor to evaluate the catalytic performance of the catalyst. 200 mg of the catalyst samples obtained from the examples and comparative examples were taken and placed in a quartz tube in the fixed bed reactor, and fixed with quartz wool. The reactants contained 2000 ppmv methane, balanced by air and nitrogen (O2 / N2 = 11:89), and the flow rate was adjusted by a mass flowmeter (Brooks 5850TR), and the total flow rate was controlled at 100 mL (STP) min −1 (Gas hourly space velocity (GHSV) = 30000 mL (STP, g -1 h -1 ). The reactor was heated from 100 °C to 500 °C at a heating rate of 2 °C min -1 . The stability test was carried out at 380 °C. The products were detected by an MKSMultiGasTM 2030 FTIR continuous gas analyzer; 2 cm 3 IR cell; liquid nitrogen-cooled HgCdTe detector) for real-time analysis. The CH4 conversion rate (X CH4 ) and CO2 yield (y CO2 ) were calculated by the following equations: In an alternative embodiment, the composite catalytic material was activated in a helium atmosphere for 1 hour, and the total flow rate in the test method was controlled at 100 mL (STP) min −1 , where the gas hourly space velocity (GHSV) was 80000 mL (STP, g -1 h -1 ).

[0071] In an alternative embodiment, the composite catalytic material is activated in a helium atmosphere for 3 hours, and the total flow rate in the test method is controlled at 100 mL (STP) min −1 , where the gas hourly space velocity (GHSV) is 120000 mL (STP, g -1 h -1 ).

[0072] The above specific embodiments do not limit the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An MFI-type heteroatom molecular sieve metal-coated composite catalytic material, characterized in that, The composite catalytic material has a hollow structure, and the composite catalytic material comprises the following components: An MFI-type molecular sieve, as a basic carrier, having a specific topological structure; Rare earth element heteroatoms, doped in the molecular sieve framework, selected from one or more of cerium and lanthanum; Noble metals, loaded on the molecular sieve, selected from one or more of palladium and platinum.

2. The MFI type heteroatom molecular sieve metal-coated composite catalytic material according to claim 1, characterized in that, The ratio of each component is: Calculated by the total mass percentage of the catalyst, the content of the rare earth element heteroatoms is 0.5% - 5%; Calculated by the total mass percentage of the catalyst, the content of the noble metals is 0.05% - 0.4%; The atomic ratio of the noble metal to the rare earth element heteroatom is 0.06 - 0.60; The molar ratio of the rare earth element heteroatom to the organic ligand is 1:1 - 1:

5.

3. Preparation method of MFI-type heteroatom molecular sieve metal-coated composite catalytic material, which is used to prepare the MFI-type heteroatom molecular sieve metal-coated composite catalytic material as described in any one of claims 1-2, and is characterized in that, It includes the following steps: S1. Using the hydrothermal synthesis method to prepare a gel substance, specifically including: i. Mix the silicon source, organic template agent and deionized water, and stir until the silicon source is completely dissolved to obtain a first mixed solution; ii. Mix the cerium source and the organic ligand, add them to deionized water, and stir until completely dissolved to obtain a second mixed solution; iii. Add the second mixed solution to the first mixed solution and stir evenly. Whether to add an aluminum source can be selected according to the target product; Do not add an aluminum source for preparing palladium / cerium-doped pure silicon molecular sieve; Add an aluminum source for preparing palladium / cerium-doped silicon-aluminum molecular sieve; Continue to stir the prepared palladium / cerium-doped pure silicon molecular sieve or the palladium / cerium-doped silicon-aluminum molecular sieve for 1 - 24 hours to obtain a gel substance; S2. Transfer the gel substance to a sealed high-pressure reactor, crystallize it at a temperature of 100 - 200 °C for 1 - 5 days; separate and collect the crystallization product, dry it and calcine it at 540 °C to obtain an MFI-type heteroatom molecular sieve containing framework cerium elements; S3. Use the MFI-type heteroatom molecular sieve as a carrier to anchor metallic palladium, and through calcination treatment, obtain a palladium / cerium-doped pure silicon molecular sieve or a palladium / cerium-doped silicon-aluminum molecular sieve catalytic material; S4. Carry out organic base treatment on the palladium / cerium-doped pure silicon molecular sieve or the palladium / cerium-doped silicon-aluminum molecular sieve catalytic material, and after centrifugal drying and calcination, obtain a hollow palladium / cerium-doped pure silicon molecular sieve or a hollow palladium / cerium-doped silicon-aluminum molecular sieve catalytic material with a hollow structure.

4. The preparation method of the MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to claim 3, characterized in that, The cerium source is one or more of cerium chloride, cerium nitrate, and cerium acetylacetonate, the silicon source is one or more of water glass, sodium silicate, methyl orthosilicate, ethyl orthosilicate, or silica sol, the organic template agent is one or more of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, and tetraethylammonium bromide, the aluminum source is one or more of aluminum chloride, aluminum sulfate, and sodium metaaluminate, the ligand is one or more of ethylenediamine, cetyltrimethylammonium bromide, ethylenediaminetetraacetic acid, acetylacetone, and sodium ethylenediaminetetraacetate, the source of the anchored metallic palladium is one or more of palladium nitrate and palladium chloride, and the organic base is one or more of tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and n-butylamine.

5. The preparation method of the MFI type heteroatom molecular sieve metal-coated composite catalytic material according to claim 4, characterized in that, The molar ratio between the rare earth element and the organic ligand is 1:1 to 1:5; in step S1, the stirring time of the first mixed solution is 3 to 10 hours, and the stirring temperature is 30 to 40 °C. In step S1, the stirring time of the second mixed solution is 5 to 30 minutes, and the stirring temperature is 30 to 40 °C; In step S1, the cerium source used is replaced with a rare earth element source, and the rare earth element is selected from one or more of cerium and lanthanum; In step S3, the anchored metallic palladium is replaced with a noble metal, and the noble metal is selected from one or more of palladium and platinum.

6. The preparation method of the MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to claim 5, wherein, When the rare earth element is lanthanum, the lanthanum source is one or more of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate; When the noble metal is platinum, the platinum source is one or more of chloroplatinic acid, tetraammineplatinum nitrate, and platinum sulfate; In step S2, the crystallization temperature is 120 to 180 °C, and the crystallization time is 72 to 120 hours; In step S4, the temperature for the treatment with the organic base is 80 to 170 °C, and the treatment time is 72 to 120 hours; In the composite catalytic material, the mass percentage of cerium content is 0.5% to 5%, and the mass percentage of palladium content is 0.05% to 0.4%.

7. The preparation method of the MFI type heteroatom molecular sieve metal-coated composite catalytic material according to claim 5, wherein the step S1 is prepared by using a mixing device, and is characterized in that The mixing device includes a reaction kettle (1), a feeding mechanism (3), a motor (2), a main shaft (9), a main stirring rod (8), and a reaction assembly (4); the reaction kettle (1) is connected to the feeding mechanism (3), the upper part of the reaction kettle (1) is rotatably connected to the main shaft (9), the main stirring rod (8) is connected to the main shaft (9), and the reaction assembly (4) is arranged inside the reaction kettle (1); The reaction assembly (4) includes a tank body (401), a feeding pipe (403), a secondary stirring rod (402), an inner cylinder (404), a liquid outlet (405), an outer cylinder (406), an annular pipe (407), and a plurality of dropping heads (408); The tank body (401) is connected to the inner wall of the reaction kettle (1), the upper part of the tank body (401) is rotatably connected to the secondary stirring rod (402), the feeding pipe (403) passes through the reaction kettle (1) and is connected to the upper part of the tank body (401), the inner cylinder (404) is connected to the lower part of the tank body (401), an outer cylinder (406) is arranged outside the inner cylinder (404), the outer cylinder (406) is connected to the bottom of the tank body (401), the liquid outlet (405) is processed on the inner cylinder (404), the outer cylinder (406) is connected to the annular pipe (407), and a plurality of the dropping heads (408) are connected to the annular pipe (407).

8. The preparation method of the MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to claim 7, characterized in that, It further includes a linkage mechanism (7); the linkage mechanism (7) includes a first gear (701), a first toothed ring (702), a limiting plate (703), a bottom plate (704), a back plate (705), a spring (706), a pawl (707), and a ratchet (708); The first gear (701) is meshed and connected with the first gear ring (702). The first gear ring (702) is rotatably connected with the limit plate (703). The limit plate (703) is connected with the inner wall of the reaction kettle (1). The first gear ring (702) is connected with the main shaft (9). The first gear (701) is connected with the bottom plate (704). The bottom plate (704) is connected with the back plate (705). The back plate (705) is connected with the ratchet pawl (707) through the spring (706). The ratchet pawl (707) is rotatably connected with the back plate (705). The ratchet pawl (707) is engaged with the ratchet wheel (708). The ratchet wheel (708) is connected with the auxiliary stirring rod (402).

9. The preparation method of the MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to claim 8, wherein, It further includes a driving mechanism (5) and a material control mechanism (6). The driving mechanism (5) is arranged between the first gear (701) and the bottom plate (704); The driving mechanism (5) includes a connecting shaft (501), a second gear ring (502), a third gear ring (503), a bracket (504), an inner ring (505), a rotating plate (506), a stop bar (507), a shaft body (508), a torsion spring (509), a lever (510) and a mounting bracket (511); The connecting shaft (501) is rotatably connected with the mounting bracket (511). The mounting bracket (511) is connected with the reaction kettle (1). The connecting shaft (501) is connected with the second gear ring (502). The second gear ring (502) is connected with the third gear ring (503). The third gear ring (503) is rotatably connected with the bracket (504). The bracket (504) is connected with the reaction kettle (1). The inner side of the third gear ring (503) is connected with the inner ring (505). The rotating plate (506) is connected with the shaft body (508). The shaft body (508) is rotatably connected with the inner ring (505). The torsion spring (509) is sleeved on the shaft body (508). Two ends of the torsion spring (509) are respectively connected with the bottom of the inner ring (505) and the lower part of the shaft body (508). The side surface of the rotating plate (506) is in contact with the stop bar (507). The stop bar (507) is connected with the inner ring (505). The stop bar (507) limits the rotating plate (506) to rotate only in one direction. The rotating plate (506) corresponds to the lever (510). The lever (510) is connected with the bottom plate (704); The material control mechanism (6) includes a convex block (601), a rod body (602), a reciprocating groove (603), a clamping block (604), two limiting rods (605), a connecting rod (606) and a cylinder body (607); The bump (601) is connected to the mounting bracket (511), the bump (601) is rotatably connected to the rod body (602), the rod body (602) is connected to the connecting shaft (501), the reciprocating groove (603) is machined on the rod body (602), the clamping block (604) is slidably connected to the reciprocating groove (603), the clamping block (604) is slidably connected to the two limiting rods (605), the two limiting rods (605) are connected to the bump (601), the clamping block (604) is connected to the cylinder body (607) through the connecting rod (606), the cylinder body (607) is arranged between the inner cylinder (404) and the outer cylinder (406), and the inner wall and the outer wall of the cylinder body (607) are respectively attached to the inner cylinder (404) and the outer cylinder (406).

10. Application of the MFI-type heteroatom molecular sieve metal-coated composite catalytic material, which is applied to the MFI-type heteroatom molecular sieve metal-coated composite catalytic material according to any one of claims 1 to 2, characterized in that: Before the reaction, the composite catalytic material is activated in a helium atmosphere for 1 to 3 hours, and then methane and air are introduced for catalytic oxidation reaction, and the gas hourly space velocity is 30,000 to 120,000 h -1 .

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