ZSM-5 nanosheet catalyst as well as preparation method and application thereof

Abstract

The invention relates to a ZSM-5 nanosheet catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts.According to the preparation method, the morphology of the catalyst is regulated and controlled through a specific silicon-aluminum ratio and a specific fluorine-aluminum ratio, so that the obtained ZSM-5 nanosheet catalyst has an excellent catalytic effect, and the catalyst has a good application prospect. The waste cable crosslinked polyethylene can be effectively degraded and recycled into a series of gaseous and liquid hydrocarbons, and high-value utilization of the waste cable crosslinked polyethylene is realized.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a ZSM-5 nanosheet catalyst, its preparation method, and its application. Background Technology

[0002] Cross-linked polyethylene (XLPE) is widely used for external insulation of power transmission lines due to its excellent electrical properties and thermal stability, and is often used as the core insulation medium for high-voltage cables. XLPE insulation is produced by thoroughly mixing polyethylene (PE) resin, cross-linking agents, stabilizers, and other additives in a high-speed mixer, then heating and melting the mixture in an extruder, and finally extruding it uniformly onto the conductor or inner shield to form an insulation layer of a specified thickness. With the continuous expansion of the use of high-voltage cables and their gradual expiration of service life, the amount of retired cables is increasing year by year. Due to the complex operating environment of cables, their insulation layer gradually ages and deteriorates under the combined effects of external factors such as light, heat, and oxygen, leading to a decline in their insulation performance. Therefore, exploring resource recycling pathways for retired XLPE cables is particularly important.

[0003] Currently, the metal conductors in cables have a mature resource recovery path, but the recycling of XLPE still faces certain technical bottlenecks. The recycling methods for XLPE outer insulation mainly include mechanical recycling, chemical recycling, and energy recovery. Mechanical recycling primarily uses physical methods to break down the cable, converting it into a series of functional fillers. Compared to traditional PE materials, the three-dimensional network structure formed by the cross-linking of XLPE molecular chains results in poor flowability, making it difficult to reprocess under traditional extrusion processes. Chemical recycling mainly includes pyrolysis and hydrocracking. These methods can decompose XLPE into smaller molecule compounds or monomers to varying degrees, further converting it into products with higher added value. Pyrolysis technology refers to the method of heating XLPE to approximately 500℃ under anaerobic conditions to decompose it. During pyrolysis, the C-C bonds of the macromolecular chains break randomly, resulting in a wide carbon number distribution in the product, making it difficult to control the product composition; increasing the pyrolysis temperature is beneficial for improving the yield of low-carbon products, but energy consumption is high. Hydrocracking technology converts the polymer into high-quality fuels through C-C bond breaking and hydrogenation reactions. Hydrocracking produces high-saturation products and exhibits less equipment corrosion, but it consumes large amounts of catalyst, and solvent / catalyst-assisted methods are prone to secondary pollution, increasing the difficulty of post-treatment. Existing recovery processes generally suffer from poor product controllability, high energy consumption and costs, or low product added value, making it difficult to achieve large-scale, efficient, and green recycling. In summary, all current technologies face the challenge of balancing economic efficiency with environmental friendliness.

[0004] Therefore, there is an urgent need to develop a method for the resource recycling of XLPE that can be modified in a mild and efficient manner, while achieving controllable product composition, low energy consumption, and high added value, so as to break through the technical bottleneck of large-scale green recycling of retired XLPE cable insulation materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a ZSM-5 nanosheet catalyst, its preparation method, and its application. The catalyst provided by this invention can effectively degrade and recycle cross-linked polyethylene from waste cables into a series of gaseous and liquid hydrocarbons, achieving high-value utilization.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a ZSM-5 nanosheet catalyst, comprising the following steps: Step (1) After stirring and reacting tetraethyl silicate (TEOS) and tetrapropylammonium hydroxide (TPAOH), the ethanol is removed and then crystallization is performed to obtain a precursor solution; Step (2) Add tetraethyl silicate and tetrapropylammonium hydroxide to the precursor solution obtained in step (1) and mix to obtain solution A; mix the aluminum salt solution and the ammonium fluoride solution to obtain solution B, wherein the molar ratio of fluoride ions to aluminum ions in solution B is (5-20):1; the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (15-40):1; Step (3) Mix solution A obtained in step (2) with solution B and carry out hydrothermal reaction. After centrifugation, washing, drying, and calcination, the ZSM-5 nanosheet catalyst is obtained.

[0007] As an embodiment of the present invention, in step (1), the mass ratio of tetraethyl silicate to tetrapropylammonium hydroxide is (2-3):(3-4).

[0008] As an embodiment of the present invention, in step (1), the tetrapropylammonium hydroxide is a tetrapropylammonium hydroxide solution, and the mass concentration of the tetrapropylammonium hydroxide solution is 20-30%.

[0009] As an embodiment of the present invention, in step (1), the temperature of the stirring reaction is 30℃-50℃ and the time is 4.5h-10h.

[0010] As an embodiment of the present invention, the stirring reaction is carried out as follows: stirring reaction at 30℃-40℃ for 4h-8h, followed by stirring reaction at 40℃-50℃ for 0.5h-2h.

[0011] As an embodiment of the present invention, in step (1), the crystallization temperature is 60℃-80℃ and the time is 36h-60h.

[0012] As an embodiment of the present invention, in step (1), the crystallization is carried out in a high-pressure reactor.

[0013] As an embodiment of the present invention, the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (18-37):1.

[0014] As an embodiment of the present invention, the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (35-37):1.

[0015] In one embodiment of the present invention, in step (2), the mass ratio of the precursor solution, tetraethyl silicate, and tetrapropylammonium hydroxide is (25-30):(8-12):(5-6.5). In another embodiment of the present invention, in step (2), the mixing temperature is 30℃-40℃, the time is 3h-6h, and the mixing is performed by stirring.

[0016] As an embodiment of the present invention, in step (2), the molar ratio of fluoride ions to aluminum ions in solution B is (7-16):1.

[0017] As an embodiment of the present invention, in step (2), the molar ratio of fluoride ions to aluminum ions in solution B is (14-16):1.

[0018] As an embodiment of the present invention, in step (2), the mass ratio of ammonium fluoride to tetrapropylammonium hydroxide is (1.2-1.6):(5-6.5).

[0019] As an embodiment of the present invention, in step (2), the aluminum salt includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride.

[0020] As an embodiment of the present invention, the aluminum salt is at least one of aluminum sulfate and aluminum nitrate.

[0021] As an embodiment of the present invention, in step (3), the temperature of the hydrothermal reaction is 160℃-180℃ and the time is 10 h-16 h.

[0022] As an embodiment of the present invention, in step (3), the washing is performed by washing with water (optionally deionized water) until neutral.

[0023] As an embodiment of the present invention, in step (3), the drying temperature is 70℃-100℃ and the time is 10 h-14 h.

[0024] As an embodiment of the present invention, in step (3), the calcination temperature is 500℃-600℃ and the time is 4 h-8 h.

[0025] As an embodiment of the present invention, in step (3), the heating rate during calcination is 2 ℃ / min - 10 ℃ / min.

[0026] Secondly, the present invention provides a ZSM-5 nanosheet catalyst prepared by the method described above.

[0027] Thirdly, the present invention provides the application of the ZSM-5 nanosheet catalyst in the catalytic recycling of cross-linked polyethylene.

[0028] As an embodiment of the present invention, the method for recycling cross-linked polyethylene catalyzed by the ZSM-5 nanosheet catalyst is as follows: the ZSM-5 nanosheet catalyst is mixed with cross-linked polyethylene and pyrolyzed under an inert atmosphere to obtain liquid and gaseous products.

[0029] As an embodiment of the present invention, the mass ratio of the cross-linked polyethylene to the ZSM-5 nanosheet catalyst is (4-6):1.

[0030] As an embodiment of the present invention, the inert atmosphere includes nitrogen, and the flow rate of the inert atmosphere is 30 mL / min-40 mL / min.

[0031] As an embodiment of the present invention, the pyrolysis temperature is 350℃-450℃ and the time is 0.5 h-1.5 h.

[0032] In one embodiment of the present invention, the cross-linked polyethylene is derived from waste cables.

[0033] As an embodiment of the present invention, the cross-linked polyethylene has a mesh size of 16-20 mesh.

[0034] The present invention has the following beneficial effects: This invention provides a ZSM-5 nanosheet catalyst, its preparation method, and its applications. By controlling the aluminum-silicon ratio and fluorine-aluminum ratio in the preparation steps, the structure and morphology of the catalyst are adjusted, resulting in an excellent catalytic cracking effect on cross-linked polyethylene. The ZSM-5 nanosheet catalyst prepared by this invention can efficiently catalyze the cross-linking of polyethylene and effectively recover a series of cracking products. It can be used for the catalytic conversion of cross-linked polyethylene from waste cables. Through the action of the ZSM-5 nanosheet solid acid catalyst, the cross-linked polyethylene from waste cables can be effectively degraded and recycled into a series of gaseous and liquid hydrocarbons, realizing the high-value utilization of cross-linked polyethylene from waste cables. Attached Figure Description

[0035] Figure 1 The images shown are TEM and EDS images of the ZSM-5 nanosheet catalyst in Example 1, where (a)-(b) are TEM images and (cf) is an EDS image. Detailed Implementation

[0036] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0037] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0038] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0039] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0040] Unless otherwise specified, all components, raw materials, or instruments used in the embodiments and comparative examples of this application are commercially available, and the components and raw materials used in each parallel experiment are the same.

[0041] In the following description, all figures disclosed herein are approximate values, regardless of whether the terms "about" or "approximately" are used in conjunction. They may vary by 1%, 2%, 5%, or sometimes 10% to 20%. Whenever a range of values ​​with a lower limit RL and an upper limit RU is disclosed, any values ​​falling within that range are specifically disclosed. Specifically, the following values ​​within this range are specifically disclosed: R = RL + k * (RU - RL), where k is a variable with a 1% increment from 1% to 100%, i.e., k is 1%, 2%, 3%, 4%, 5%, ..., 50%, 51%, 52%, ..., 95%, 96%, 97%, 98%, 99%, or 100%. Furthermore, any range of values ​​defined by the two R values ​​as defined above are also specifically disclosed.

[0042] General definition The term "crosslinked polyethylene" refers to modified polyethylene in which the polyethylene molecular chains form a three-dimensional network structure through chemical or physical crosslinking.

[0043] The term "ZSM-5 nanosheets" refers to aluminosilicate zeolite molecular sieves with an MFI topology, whose crystals are oriented and controlled to form ultrathin two-dimensional sheet-like morphologies. Typical characteristics include a thickness of only a few nanometers to tens of nanometers along the b-axis, while the in-plane size can reach hundreds of nanometers. At the same time, it retains the inherent ten-membered ring cross-micropore system of ZSM-5 (straight cylindrical pores + Z-shaped transverse pores). It is different from traditional micron-sized ZSM-5 bulk crystals and ordinary nanoparticles, and belongs to hierarchical porous molecular sieves (mesopores formed by stacking micropores and nanosheets).

[0044] The term "crystallization" refers to the reaction process in which a pre-prepared amorphous (non-crystalline) silicate / aluminate precursor sol or gel is gradually transformed into zeolite molecular sieve crystals with regular crystal structure and perfect crystallization through nucleation and growth in a closed reactor under certain temperature and autogenous pressure.

[0045] The term "precursor solution" refers to a homogeneous liquid system containing all or most of the chemical components required to form the target product, and in which the components are uniformly dispersed in molecular, ionic, or colloidal states.

[0046] To address the problems existing in the resource utilization of cross-linked polyethylene from waste cables in the prior art, and to achieve a resource recycling method for XLPE with controllable product composition, low energy consumption, and high added value, the first aspect of this invention provides a method for preparing a ZSM-5 nanosheet catalyst, comprising the following steps: Step (1) After stirring and reacting tetraethyl silicate (TEOS) and tetrapropylammonium hydroxide (TPAOH), the ethanol is removed and then crystallization is performed to obtain a precursor solution; Step (2) Add tetraethyl silicate and tetrapropylammonium hydroxide to the precursor solution obtained in step (1) and mix to obtain solution A; Solution B is obtained by mixing aluminum salt solution and ammonium fluoride solution, wherein the molar ratio of fluoride ions to aluminum ions in solution B is (5-20):1; The ratio of the total molar amount of tetraethyl silicate in step (1) and step (2) to the molar amount of aluminum ions in solution B is (15-40):1; Step (3) Mix solution A obtained in step (2) with solution B and carry out hydrothermal reaction. After centrifugation, washing, drying, and calcination, the ZSM-5 nanosheet catalyst is obtained.

[0047] The preparation method of this invention controls the morphology of the catalyst by using specific silicon-aluminum ratio and fluorine-aluminum ratio, thereby obtaining ZSM-5 nanosheet catalyst with excellent catalytic effect. It can effectively degrade and recycle cross-linked polyethylene from waste cables into a series of gaseous and liquid hydrocarbons, realizing the high-value utilization of cross-linked polyethylene from waste cables.

[0048] The formation of structure-directed initial nuclei or oligomeric species in step (1) of this invention is a key precursor for constructing ZSM-5 nanosheet structures. By first forming regular initial nuclei, and then further expanding the silicon source and introducing structure-directing agents, a stable and uniform raw material basis can be provided for subsequent crystallization growth, ensuring the controllability of crystal morphology, wherein: The tetraethyl silicate used is a high-purity reagent, free of metal impurities, which can ensure the purity and catalytic activity of the final molecular sieve; the hydrolysis rate of tetraethyl silicate to generate silicic acid is controllable, which is beneficial to forming a uniform precursor solution with controllable size.

[0049] TPA in tetrapropylammonium hydroxide + The size and shape of the cations are highly matched to the pore structure of ZSM-5.

[0050] Ammonium fluoride (NH4F) hydrolyzes in aqueous solution to provide F. - and NH4 + NH4 + It has minimal impact on the system's pH and leaves no residue after calcination; if other fluoride salts such as NaF or KF are used, they can provide F. - However, it introduces additional alkali metal ions, which severely occupy the acidic sites of the molecular sieve, leading to a significant reduction in the acidity of the prepared catalyst or even its failure.

[0051] The amount of aluminum source added directly determines the acidity of the catalyst, while the introduction of ammonium fluoride has the dual role of mineralizer and morphology regulator, and has an important influence on the crystal growth path and the distribution of acidic sites.

[0052] This invention has discovered that when aluminum ions and tetraethyl silicate meet the specific ratio mentioned above, the crystal growth kinetics of ZSM-5 nanosheets can be effectively regulated, promoting the formation of a sheet-like structure with high specific surface area and suitable acid strength distribution, thereby significantly improving the catalytic cracking performance of cross-linked polyethylene.

[0053] When the ratio of aluminum ions to tetraethyl silicate is too low, it can easily lead to thickening of molecular sieve layers or uneven morphology, and a significant decrease in specific surface area; when the ratio is too high, it may inhibit normal crystal growth and affect the crystallinity and yield of the final product.

[0054] Furthermore, the specific high fluorine-to-aluminum ratio employed in this invention can effectively suppress excessive crystal growth along the b-axis, which is more conducive to the formation of two-dimensional sheet-like structures. Simultaneously, this fluorine-to-aluminum ratio can further optimize the acidity distribution of the catalyst by regulating the coordination and distribution state of aluminum, reducing side reactions caused by excessive aggregation of strong acid sites, and ultimately obtaining a ZSM-5 nanosheet catalyst with excellent catalytic degradation performance of cross-linked polyethylene.

[0055] For example, the ratio of the total molar amount of tetraethyl silicate in step (1) and step (2) to the molar amount of aluminum ions in solution B can be: 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, 26:1, 27:1, 28:1, 29:1, 30:1, 31:1, 32:1, 33:1, 34:1, 35.0:1, 35.1:1, 35.2:1, 35.3:1, 35.4:1, 35 The range of values ​​for one or any two of the following: 0.5:1, 35.6:1, 35.7:1, 35.8:1, 35.9:1, 36.0:1, 36.1:1, 36.2:1, 36.3:1, 36.4:1, 36.5:1, 36.6:1, 36.7:1, 36.8:1, 36.9:1, 37.0:1, 38:1, 39:1, 40:1.

[0056] In some embodiments, in step (1), the mass ratio of tetraethyl silicate to tetrapropylammonium hydroxide is (2-3):(3-4).

[0057] For example, in step (1), the mass ratio of tetraethyl silicate to tetrapropylammonium hydroxide can be: The range of values ​​for one or any two of the following: 1:1, 10:14.1, 2.5:3.5, 2:3, 2:3.5, 1:2.

[0058] In some embodiments, in step (1), the tetrapropylammonium hydroxide is a tetrapropylammonium hydroxide solution with a mass concentration of 20-30%.

[0059] For example, in step (1), the mass concentration of the tetrapropylammonium hydroxide solution can be: The range of one or any two of the following: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, and 30%.

[0060] In some embodiments, in step (1), the temperature of the stirring reaction is 30°C-50°C and the time is 4.5h-10h.

[0061] For example, in step (1), the temperature of the stirring reaction can be: 30.0℃, 30.5℃, 31.0℃, 31.5℃, 32.0℃, 32.5℃, 33.0℃, 33.5℃, 34.0℃, 34.5℃, 35.0℃, 35.5℃, 36.0℃, 36.5℃, 37.0℃, 37.5℃, 38.0℃, 38.5℃, 39.0℃, 39.5℃, 40.0℃, 40. The range of one or any two of the following: 5℃, 41.0℃, 41.5℃, 42.0℃, 42.5℃, 43.0℃, 43.5℃, 44.0℃, 44.5℃, 45.0℃, 45.5℃, 46.0℃, 46.5℃, 47.0℃, 47.5℃, 48.0℃, 48.5℃, 49.0℃, 49.5℃, and 50.0℃.

[0062] For example, in step (1), the stirring reaction time can be: The range of one or any two of the following values: 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8.0h, 8.5h, 9.0h, 9.5h, and 10.0h.

[0063] In one embodiment, the stirring reaction is carried out by stirring at 30℃-40℃ for 4h-8h, followed by stirring at 40℃-50℃ for 0.5h-2h.

[0064] In some embodiments, in step (1), the crystallization temperature is 60°C-80°C and the time is 36h-60h.

[0065] For example, in step (1), the crystallization temperature can be: 60.0℃, 60.5℃, 61.0℃, 61.5℃, 62.0℃, 62.5℃, 63.0℃, 63.5℃, 64.0℃, 64.5℃, 65.0℃, 65.5℃, 66.0℃, 66.5℃, 67.0℃, 67.5℃, 68.0℃, 68.5℃, 69.0℃, 69.5℃, 70.0℃, 70. The range of one or any two of the following: 5℃, 71.0℃, 71.5℃, 72.0℃, 72.5℃, 73.0℃, 73.5℃, 74.0℃, 74.5℃, 75.0℃, 75.5℃, 76.0℃, 76.5℃, 77.0℃, 77.5℃, 78.0℃, 78.5℃, 79.0℃, 79.5℃, and 80.0℃; For example, in step (1), the crystallization time can be: 36.0h, 36.5h, 37.0h, 37.5h, 38.0h, 38.5h, 39.0h, 39.5h, 40.0h, 40.5h, 41.0h, 41.5h, 42.0 h, 42.5h, 43.0h, 43.5h, 44.0h, 44.5h, 45.0h, 45.5h, 46.0h, 46.5h, 47.0h, 47.5h, 48.0h, 48. The range of one or any two of the following values: 5h, 49.0h, 49.5h, 50.0h, 50.5h, 51.0h, 51.5h, 52.0h, 52.5h, 53.0h, 53.5h, 54.0h, 54.5h, 55.0h, 55.5h, 56.0h, 56.5h, 57.0h, 57.5h, 58.0h, 58.5h, 59.0h, 59.5h, and 60.0h.

[0066] In some embodiments, the crystallization in step (1) is carried out in a high-pressure reactor.

[0067] In some embodiments, the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (18-37):1.

[0068] In some embodiments, the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (35-37):1.

[0069] When the aluminum-silicon ratio meets the above requirements, the catalyst can exhibit excellent catalytic performance.

[0070] In some embodiments, in step (2), the mass ratio of the precursor solution, tetraethyl silicate and tetrapropylammonium hydroxide is (25-30):(8-12):(5-6.5).

[0071] In some embodiments, in step (2), the mixing temperature is 30°C-40°C and the time is 3h-6h, and the mixing is carried out by stirring.

[0072] For example, in step (2), the mixing temperature can be: 30℃-40℃ can be a range of one or any two of the following: 30.0℃, 30.5℃, 31.0℃, 31.5℃, 32.0℃, 32.5℃, 33.0℃, 33.5℃, 34.0℃, 34.5℃, 35.0℃, 35.5℃, 36.0℃, 36.5℃, 37.0℃, 37.5℃, 38.0℃, 38.5℃, 39.0℃, 39.5℃, and 40.0℃. For example, in step (2), the mixing time can be: The range of one or any two of 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, and 6h.

[0073] For example, in step (2), the molar ratio of fluoride ions to aluminum ions in solution B can be: The range of values ​​for one or any two of the following: 5.0:1, 5.5:1, 6.0:1, 6.5:1, 7.0:1, 7.5:1, 8.0:1, 8.5:1, 9.0:1, 9.5:1, 10.0:1, 10.5:1, 11.0:1, 11.5:1, 12.0:1, 12.5:1, 13.0:1, 13.5:1, 14.0:1, 14.5:1, 15.0:1, 15.5:1, 16.0:1, 16.5:1, 17.0:1, 17.5:1, 18.0:1, 18.5:1, 19.0:1, 19.5:1, and 20.0:1.

[0074] In some embodiments, in step (2), the molar ratio of fluoride ions to aluminum ions in solution B is (7-16):1.

[0075] In some embodiments, in step (2), the molar ratio of fluoride ions to aluminum ions in solution B is (14-16):1.

[0076] When the fluorine-aluminum ratio meets the above requirements, the structure of the catalyst can be controlled, enabling the catalyst to have excellent catalytic cracking effect on cross-linked polyethylene.

[0077] In some embodiments, in step (2), the mass ratio of ammonium fluoride to tetrapropylammonium hydroxide is (1.2-1.6):(5-6.5).

[0078] For example, in step (2), the mass ratio of ammonium fluoride to tetrapropylammonium hydroxide can be: The range of one or any two of the following: 1.2:5, 1.2:5.5, 1.2:6, 1.2:6.5, 1.3:5, 1.3:5.5, 1.3:6, 1.3:6.5, 1.4:5, 1.4:5.5, 1.4:6, 1.4:6.5, 1.5:5, 1.5:5.5, 1.5:6, 1.5:6.5, 1.6:5, 1.6:5.5, 1.6:6, 1.6:6.5.

[0079] In some embodiments, in step (2), the aluminum salt includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride.

[0080] In some embodiments, the aluminum salt is at least one of aluminum sulfate and aluminum nitrate.

[0081] This invention has found that aluminum sulfate and aluminum nitrate have superior effects compared to aluminum chloride.

[0082] In some embodiments, in step (3), the temperature of the hydrothermal reaction is 160°C-180°C and the time is 10 h-16 h.

[0083] For example, in step (3), the temperature of the hydrothermal reaction can be: 160.0℃, 160.5℃, 161.0℃, 161.5℃, 162.0℃, 162.5℃, 163.0℃, 163.5℃, 164.0℃, 164.5℃, 165.0℃, 165.5℃, 166.0℃, 166.5℃, 167.0℃, 167.5℃, 168.0℃, 168.5℃, 169.0℃, 169.5℃, 170.0℃, 170 The range of one or any two of the following: 0.5℃, 171.0℃, 171.5℃, 172.0℃, 172.5℃, 173.0℃, 173.5℃, 174.0℃, 174.5℃, 175.0℃, 175.5℃, 176.0℃, 176.5℃, 177.0℃, 177.5℃, 178.0℃, 178.5℃, 179.0℃, 179.5℃, and 180.0℃.

[0084] For example, in step (3), the hydrothermal reaction time can be: The range of one or any two of the following: 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, 14h, 14.5h, 15h, 15.5h, and 16h.

[0085] In some embodiments, in step (3), the washing is performed by washing with water (optionally deionized water) until neutral.

[0086] In some embodiments, in step (3), the drying temperature is 70°C-100°C and the time is 10 h-14 h.

[0087] For example, in step (3), the drying temperature can be: 70.0℃, 70.5℃, 71.0℃, 71.5℃, 72.0℃, 72.5℃, 73.0℃, 73.5℃, 74.0℃, 74.5℃, 75.0℃, 75.5℃, 76.0℃, 76.5℃, 77.0℃, 77.5℃, 78.0℃, 78.5℃, 79.0℃, 79.5℃, 80.0℃, 80.5℃, 81.0℃, 81.5℃, 82.0℃, 82.5℃, 83.0℃, 83.5℃, 84.0℃, 84.5℃, 85.0℃, 85.5℃ The range of one or any two of the following: ℃, 86.0℃, 86.5℃, 87.0℃, 87.5℃, 88.0℃, 88.5℃, 89.0℃, 89.5℃, 90.0℃, 90.5℃, 91.0℃, 91.5℃, 92.0℃, 92.5℃, 93.0℃, 93.5℃, 94.0℃, 94.5℃, 95.0℃, 95.5℃, 96.0℃, 96.5℃, 97.0℃, 97.5℃, 98.0℃, 98.5℃, 99.0℃, 99.5℃, and 100.0℃; For example, in step (3), the drying time can be: The range of one or any two of 10h, 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h, and 14h.

[0088] In some embodiments, in step (3), the calcination temperature is 500℃-600℃ and the time is 4 h-8 h.

[0089] For example, in step (3), the calcination temperature can be: The range of one or any two of the following temperatures: 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, 535℃, 540℃, 545℃, 550℃, 555℃, 560℃, 565℃, 570℃, 575℃, 580℃, 585℃, 590℃, 595℃, and 600℃. For example, in step (3), the calcination time can be: The range of one or any two of 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, and 8h.

[0090] In some embodiments, in step (3), the heating rate during calcination is 2 ℃ / min - 10 ℃ / min.

[0091] For example, in step (3), the heating rate during calcination can be: The range of one or any two of the following: 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min, 6℃ / min, 6.5℃ / min, 7℃ / min, 7.5℃ / min, 8℃ / min, 8.5℃ / min, 9℃ / min, 9.5℃ / min, and 10℃ / min.

[0092] The second aspect of the present invention provides a ZSM-5 nanosheet catalyst prepared by the above-mentioned method.

[0093] The ZSM-5 nanosheet catalyst prepared by the method of this invention can efficiently catalyze crosslinking of polyethylene and effectively recover a series of pyrolysis products, and can be used for the catalytic conversion of crosslinked polyethylene from waste cables.

[0094] The third aspect of this invention provides the application of the above-mentioned ZSM-5 nanosheet catalyst in the catalytic recycling of cross-linked polyethylene.

[0095] Through the action of ZSM-5 nanosheet solid acid catalyst, cross-linked polyethylene from waste cables can be degraded and recycled into a series of gaseous and liquid hydrocarbons, realizing the high-value utilization of cross-linked polyethylene from waste cables.

[0096] In some embodiments, the method for recycling cross-linked polyethylene using the ZSM-5 nanosheet catalyst is as follows: the ZSM-5 nanosheet catalyst is mixed with cross-linked polyethylene and pyrolyzed under an inert atmosphere to obtain liquid and gaseous products.

[0097] In some embodiments, the mass ratio of the cross-linked polyethylene to the ZSM-5 nanosheet catalyst is (4-6):1.

[0098] For example, the mass ratio of the cross-linked polyethylene to the ZSM-5 nanosheet catalyst can be: The range of one or any two of the following values: 4.0:1, 4.1:1, 4.2:1, 4.3:1, 4.4:1, 4.5:1, 4.6:1, 4.7:1, 4.8:1, 4.9:1, 5.0:1, 5.1:1, 5.2:1, 5.3:1, 5.4:1, 5.5:1, 5.6:1, 5.7:1, 5.8:1, 5.9:1, and 6.0:1.

[0099] In some embodiments, the inert atmosphere comprises nitrogen, and the flow rate of the inert atmosphere is 30 mL / min to 40 mL / min.

[0100] For example, the flow rate of the inert atmosphere can be: The range of one or any two of the following: 30.0 mL / min, 30.5 mL / min, 31.0 mL / min, 31.5 mL / min, 32.0 mL / min, 32.5 mL / min, 33.0 mL / min, 33.5 mL / min, 34.0 mL / min, 34.5 mL / min, 35.0 mL / min, 35.5 mL / min, 36.0 mL / min, 36.5 mL / min, 37.0 mL / min, 37.5 mL / min, 38.0 mL / min, 38.5 mL / min, 39.0 mL / min, 39.5 mL / min, and 40.0 mL / min.

[0101] In some embodiments, the pyrolysis temperature is 350°C-450°C and the time is 0.5 h-1.5 h.

[0102] For example, the pyrolysis temperature can be: The range of one or any two of the following: 350℃, 355℃, 360℃, 365℃, 370℃, 375℃, 380℃, 385℃, 390℃, 395℃, 400℃, 405℃, 410℃, 415℃, 420℃, 425℃, 430℃, 435℃, 440℃, 445℃, and 450℃.

[0103] For example, the pyrolysis time can be: The range of values ​​for one or both of 0.5 h, 1 h, and 1.5 h.

[0104] In some of these embodiments, the cross-linked polyethylene is derived from waste cables.

[0105] In some embodiments, the cross-linked polyethylene has a mesh size of 16-20.

[0106] For example, the mesh count of the cross-linked polyethylene can be: The range of one or any two of the following: 16 mesh, 17 mesh, 18 mesh, 19 mesh, and 20 mesh.

[0107] The following uses the preparation method of ZSM-5 nanosheet catalyst as an example and combines specific embodiments to illustrate the ZSM-5 nanosheet catalyst and its preparation method of the present invention. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0108] Example 1 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to obtain a mixture solution. The resulting mixture solution was transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution with a total mass of 24.1 g. (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.86 g of Al2(SO4)3·18H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 1.43 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain an ammonium fluoride solution. Mix the aluminum salt solution with the ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0109] Example 2 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution; (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.623 g of AlCl3·6H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 1.43 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain an ammonium fluoride solution. Mix the aluminum salt solution with the ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0110] Example 3 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was then transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution. (2) Weigh 6 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 1.72 g of Al2(SO4)3·18H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 2.86 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain ammonium fluoride solution. Mix aluminum salt solution with ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0111] Example 4 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was then transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution. (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.86 g of Al2(SO4)3·18H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 0.48 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain ammonium fluoride solution. Mix aluminum salt solution with ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0112] Example 5 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was then transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution. (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.97 g of Al(NO3)3·9H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 1.43 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain an ammonium fluoride solution. Mix the aluminum salt solution with the ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0113] Comparative Example 1 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: Weigh 3 g of commercially available HZSM-5 and add 60 mL of 1 mol / L NH4Cl solution. Stir at room temperature for 3 h, centrifuge the system and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0114] Comparative Example 2 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was then transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution. (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.43 g of Al2(SO4)3·18H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 0.715 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain ammonium fluoride solution. Mix aluminum salt solution with ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0115] Comparative Example 3 A method for preparing a ZSM-5 nanosheet catalyst includes the following steps: (1) Weigh 10 g of tetraethyl silicate (TEOS) and 14.1 g of tetrapropylammonium hydroxide (TPAOH) and mix them. Stir at 35°C for 6 h and then at 45°C for 1 h to allow the reaction to proceed fully and remove the generated ethanol to obtain a mixed solution. The resulting mixture solution was then transferred to a high-pressure reactor and reacted at 70°C for 48 h to obtain a precursor solution. (2) Weigh 10 g of TEOS and 5.7 g of TPAOH, dissolve them in 24.1 g of precursor solution and stir at 35°C for 4 h to obtain solution A; Weigh 0.86 g of Al2(SO4)3·18H2O and dissolve it in 2 mL of deionized water. Stir for 5 min to obtain an aluminum salt solution. Weigh 2.86 g of NH4F and dissolve it in 8 mL of deionized water. Stir for 5 min to obtain ammonium fluoride solution. Mix aluminum salt solution with ammonium fluoride solution and stir for 10 min to obtain solution B. (3) Mix solution A and solution B and stir for 20 min and transfer to a high-pressure reactor. React at 170℃ for 12 h and then centrifuge the product and collect the precipitate. The precipitate was washed with deionized water until neutral and dried at 80 °C for 12 h. The dried product was heated from 20 °C to 550 °C in air at a heating rate of 5 °C / min and calcined at 550 °C for 6 h. It was then naturally cooled to obtain the ZSM-5 nanosheet catalyst.

[0116] Characterization and testing: Figure 1 The images shown are TEM and EDS images of the ZSM-5 nanosheet catalyst in Example 1, where (a) and (b) are TEM images and (cf) is an EDS image.

[0117] from Figure 1 As can be seen from the TEM images (a) and (b), the obtained catalyst exhibits a clear two-dimensional nanosheet morphology with a sheet thickness of approximately 10-20 nm and a lateral size in the range of 100-200 nm. Furthermore, there is moderate stacking between the sheets, forming a mesoporous structure that is conducive to the diffusion of macromolecules.

[0118] Figure 1The EDS elemental distribution diagram (cf) shows that Si, Al, and O are uniformly distributed within the nanosheet region without significant agglomeration, confirming that aluminum species have been successfully and uniformly incorporated into the ZSM-5 molecular sieve framework. This uniform aluminum distribution is conducive to the formation of acidic sites of moderate strength and quantity, which is a key structural feature enabling the catalyst to efficiently cleave cross-linked polyethylene and control product selectivity.

[0119] The ZSM-5 nanosheet catalysts obtained in the examples and comparative examples were used for the catalytic recovery of cross-linked polyethylene, as follows: (1) Separate XLPE from waste cables, collect and screen out 16-20 mesh XLPE particles; (2) Weigh 1500 mg of XLPE particles and 300 mg of ZSM-5 nanosheet catalyst, mix them evenly, and heat them from 20°C to 400°C at a heating rate of 10°C / min under a N2 flow rate of 35 mL / min and keep them at that temperature for 60 min; collect the liquid product; collect the uncondensed gaseous product using an 8L gas bag.

[0120] The catalytic cracking recovery rates of cross-linked polyethylene by the ZSM-5 nanosheet catalysts obtained in the examples and comparative examples, as well as the proportions of high-value products obtained from the catalytic cracking, are shown in Tables 1 and 2. The testing methods for the high-value products are as follows: Commercially available ethylene, propylene, butene, benzene, toluene, and xylene were analyzed by gas chromatography (GC) using commercially available monomers. The chromatographic conditions were as follows: FID detector: 180°C; column: Al₂O₃ / KCl, 50 m × 0.53 mm × 20 μm; temperature programming: 50°C for 3 min, then ramp to 150°C and hold for 5 min, with a ramp rate of 5°C / min; carrier gas: high-purity nitrogen.

[0121] Table 1. Catalytic cracking recovery rate of cross-linked polyethylene Table 2. Proportion of high-value products from the catalytic cracking of cross-linked polyethylene As can be seen from Tables 1 and 2: The catalyst in Example 1 exhibits excellent crosslinked polyethylene conversion, a high conversion rate attributed to the high efficiency of the nanosheet structure and a suitable acid content. The high liquid yield and BTX selectivity indicate an appropriate acid strength distribution, effectively cleaving macromolecules while allowing timely product diffusion and desorption, resulting in moderate secondary reactions to generate high-value aromatics, without excessive condensation and carbon deposition. The 42.2% low-carbon olefin selectivity indicates well-controlled hydrogen transfer reactions.

[0122] In Example 2, aluminum chloride was used as the aluminum source.- Defects may be introduced during the crystallization process, or some residual Cl may remain. - The poisoning of strong acid sites led to a decrease in the overall efficiency of active sites.

[0123] In Example 3, the increased aluminum content resulted in extremely high density and activity of strong acid sites, leading to a higher conversion rate. However, the strong acid readily catalyzes deep dehydrogenation and condensation reactions, resulting in severe carbon buildup and a risk of rapid catalyst deactivation.

[0124] Example 4 showed a better conversion rate, indicating that the amount of acid inside the catalyst and the amount used in Example 3 were sufficient. However, the large XLPE molecules had difficulty diffusing into the micropores of the cubic ZSM-5 particles, and the reaction mainly occurred on a small number of acid sites on the outer surface of the particles. This shallow pyrolysis tends to generate gas.

[0125] The catalytic activity of the conventionally prepared hydrogen-type ZSM-5 molecular sieve in Comparative Example 1 was significantly lower than that in the Example.

[0126] In Comparative Example 2, the amount of aluminum added was relatively small, which directly led to insufficient acidity in the catalyst. The limited acid centers could only initially break down the polymer into small molecule gases, and there were not enough acid centers to support further carbocation reactions such as isomerization and aromatization to generate liquid products.

[0127] In Comparative Example 3, excessive addition of fluoride ions disrupts the integrity of the crystal structure, generating non-selective strong acid sites and defects, leading to a decrease in conversion rate. Furthermore, partial structural damage reduces the effective acid content, but the strong acid sites promote hydrogen transfer, causing alkenes to convert into alkanes and aromatics.

[0128] In summary, this application provides a ZSM-5 nanosheet catalyst, its preparation method, and its application. By controlling the aluminum-silicon ratio and fluorine-aluminum ratio during the preparation process, the catalyst's structure and morphology can be precisely controlled, thereby endowing the catalyst with excellent catalytic cracking performance of cross-linked polyethylene. The ZSM-5 nanosheet catalyst prepared by this invention can efficiently catalyze the cracking reaction of cross-linked polyethylene and achieve the effective recovery of a series of cracking products, making it suitable for the catalytic conversion of cross-linked polyethylene from waste cables. Under the action of this ZSM-5 nanosheet solid acidic catalyst, cross-linked polyethylene from waste cables can be effectively degraded and recycled into various gaseous and liquid hydrocarbon products, ultimately achieving high-value resource utilization of cross-linked polyethylene from waste cables.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a ZSM-5 nanosheet catalyst, characterized in that, Includes the following steps: Step (1) After stirring and reacting tetraethyl silicate and tetrapropylammonium hydroxide, the ethanol is removed, and then crystallization is carried out to obtain a precursor solution; Step (2) Add tetraethyl silicate and tetrapropylammonium hydroxide to the precursor solution obtained in step (1) and mix to obtain solution A; mix the aluminum salt solution and the ammonium fluoride solution to obtain solution B, wherein the molar ratio of fluoride ions to aluminum ions in solution B is (5-20):1; the ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (15-40):1; Step (3) Mix solution A obtained in step (2) with solution B and carry out hydrothermal reaction. After centrifugation, washing, drying, and calcination, the ZSM-5 nanosheet catalyst is obtained.

2. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, The ratio of the total molar amount of tetraethyl silicate in step (1) and the total molar amount of tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (18-37):1; and / or, in step (1), the mass ratio of tetraethyl silicate to tetrapropylammonium hydroxide is (2-3):(3-4).

3. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, In step (1), the temperature of the stirring reaction is 30℃-50℃ and the time is 4.5h-10h; and / or, the temperature of the crystallization is 60℃-80℃ and the time is 36h-60h; and / or, the ratio of the total molar amount of tetraethyl silicate in step (1) and tetraethyl silicate in step (2) to the molar amount of aluminum ions in solution B is (35-37):

1.

4. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, In step (2), the mass ratio of the precursor solution, tetraethyl silicate and tetrapropylammonium hydroxide is (25-30):(8-12):(5-6.5); and / or, the molar ratio of fluoride ions to aluminum ions in solution B is (7-16):

1.

5. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, In step (2), the mixing temperature is 30℃-40℃ and the time is 3h-6h; and / or, in step (2), the mass ratio of ammonium fluoride to tetrapropylammonium hydroxide is (1.2-1.6):(5-6.5); and / or, the aluminum salt includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride; and / or, the molar ratio of fluoride ions to aluminum ions in solution B is (14-16):

1.

6. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, In step (3), the temperature of the hydrothermal reaction is 160℃-180℃ and the time is 10 h-16 h.

7. The method for preparing the ZSM-5 nanosheet catalyst according to claim 1, characterized in that, In step (3), the drying temperature is 70℃-100℃ and the time is 10 h-14 h; and / or, the calcination temperature is 500℃-600℃ and the time is 4 h-8 h; and / or, the heating rate during calcination is 2 ℃ / min-10℃ / min.

8. The ZSM-5 nanosheet catalyst prepared by the method of any one of claims 1-7.

9. The application of the ZSM-5 nanosheet catalyst according to claim 8 in the catalytic recycling of cross-linked polyethylene.

10. The application of the ZSM-5 nanosheet catalyst according to claim 9 in the catalytic recycling of cross-linked polyethylene, characterized in that, The method for recycling cross-linked polyethylene using the ZSM-5 nanosheet catalyst is as follows: the ZSM-5 nanosheet catalyst is mixed with cross-linked polyethylene and pyrolyzed under an inert atmosphere to obtain liquid and gaseous products.

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