An EMT / FAU eutectic molecular sieve catalyst and its preparation method and application

Abstract

The present invention relates to the technical field of polyolefin degradation, and in particular to an EMT / FAU eutectic molecular sieve catalyst, a preparation method and an application. The EMT / FAU eutectic molecular sieve catalyst is obtained by physical mixing an acidic molecular sieve and a Pt-loaded TS-1 molecular sieve, and the mass ratio of the acidic molecular sieve to the Pt-loaded TS-1 molecular sieve is 1:1. The present invention obtains an acidic molecular sieve by exchanging ammonium ions on the EMT / FAU eutectic molecular sieve; utilizes the TS-1 molecular sieve to encapsulate Pt to provide abundant metal hydrogenation sites; constructs an acidic site-metal series system by the acidic molecular sieve and the Pt-loaded TS-1 molecular sieve, which can convert polyethylene into short-chain alkanes under mild conditions, making the distribution of liquid products more concentrated, and solving the problems of excessively high hydrogen pressure, high energy consumption and non-concentrated distribution of reaction products in the polyethylene hydrocracking reaction of existing molecular sieve catalysts.

Description

Technical Field

[0001] The present invention relates to the technical field of polyolefin degradation, and in particular to an EMT / FAU eutectic molecular sieve catalyst, a preparation method and an application thereof. Background Art

[0002] Polyolefins, as one of the most consumed categories of plastics, are widely used in packaging, construction, medicine and health care and other fields. Due to the non-degradability of polyolefins, they cause serious problems to the environment. At present, most plastic waste is disposed of by landfill or incineration, which not only produces greenhouse gases but also causes environmental pollution. Converting plastic waste into the original plastic through mechanical recycling usually leads to the degradation of its physical and mechanical properties and reduces its value. In recent years, chemical catalytic conversion has become a promising solution, which can efficiently convert plastic waste into high-purity and high-value-added chemicals such as liquid fuels and naphtha through the action of catalysts, promoting the development of the circular economy.

[0003] Research has shown that the catalytic hydrocracking of polyolefins can effectively crack polyethylene long chains using bifunctional catalysts, such as molecular sieve and metal composite systems. For example, the process of catalytic hydrocracking of polyethylene includes: polyethylene adsorbs onto metal sites, which dehydrogenate to form olefin intermediates; the olefin intermediates desorb and diffuse to Brønsted acid sites, converting to carbon cation reaction intermediates; the carbon cation reaction intermediates then undergo isomerization and β-cracking, and then diffuse back to the metal sites for hydrogenation into linear and branched alkanes. Brønsted acid sites, commonly referred to as Brønsted acid sites, can release protons to participate in catalytic reactions in porous materials such as molecular sieves.

[0004] Currently, molecular sieve catalysts are mostly used for the catalytic decomposition of polyethylene due to their unique topological structure. For example, prior art 1: Brandon C. Vance et al. published a paper in the Journal of Chemical Engineering, Issue 487, 2024, with the paper number 150468. This study developed a Ni / Beta catalyst for polyolefin hydrocracking. In this study, the researchers loaded metallic Ni on Beta molecular sieve to achieve catalytic hydrocracking of polyethylene, achieving complete decomposition of low-density polyethylene within 12 hours at 250°C and 6 MPa H2. However, the reaction conditions for using this Ni / Beta catalyst for polyolefin hydrocracking are relatively harsh, and the H2 pressure is too high, which not only increases the risk, but also increases production costs and requires a long reaction time.

[0005] Prior Art 2: CN119215967A discloses a trace metal / molecular sieve catalyst that modifies a conventional microporous molecular sieve by mechanical ball milling and loads trace metals onto it, thereby improving the accessibility of the long-chain alkane molecules of waste polyolefins to the loaded metal particles and the acidic sites of the molecular sieve, thereby achieving maximum conversion of polyolefins into isomerized fuels while saving metal loading. However, when using this trace metal / molecular sieve catalyst to catalyze waste polyolefins to produce isomerized fuels at low temperatures, the resulting products are widely distributed, ranging from C5 to C 40 , the product value is low and the cost of separation and purification is high. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides an EMT / FAU eutectic molecular sieve catalyst, a preparation method and an application thereof.

[0007] The present invention designs an EMT / FAU eutectic molecular sieve catalyst with low required hydrogen pressure, concentrated distribution of liquid products, high added value, and high efficiency in catalyzing the degradation of waste polyolefins. The catalyst can effectively decompose waste polyolefin plastics and has universal applicability, thereby solving the problems of existing molecular sieve catalysts in polyethylene hydrocracking reactions such as excessively high hydrogen pressure, high energy consumption, and non-concentrated distribution of reaction products.

[0008] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0009] The first aspect of the present invention provides an EMT / FAU eutectic molecular sieve catalyst, which is obtained by physically mixing an acidic molecular sieve and a Pt-loaded TS-1 molecular sieve, wherein the mass ratio of the acidic molecular sieve to the Pt-loaded TS-1 molecular sieve is 1:1; the acidic molecular sieve is obtained by subjecting the EMT / FAU eutectic molecular sieve to ion exchange in an inorganic ammonium salt solution to introduce ammonium ions to increase Brønsted acid sites, and then drying and calcining to obtain the acidic molecular sieve.

[0010] The present invention obtains an acidic molecular sieve by exchanging ammonium ions on the EMT / FAU eutectic molecular sieve to increase Brønsted acid sites; utilizes TS-1 molecular sieve to encapsulate Pt to provide abundant metal hydrogenation sites; and constructs an acidic site-metal series system by combining the acidic molecular sieve with the Pt-loaded TS-1 molecular sieve. Polyethylene can be converted into short-chain alkanes under mild conditions, resulting in a more concentrated distribution of liquid products. This solves the problems of excessively high hydrogen pressure, high energy consumption, and non-concentrated distribution of reaction products in polyethylene hydrocracking reactions caused by existing molecular sieve catalysts.

[0011] The EMT / FAU eutectic molecular sieve catalyst of the present invention can reduce the hydrogen pressure in the polyethylene hydrocracking reaction, while efficiently catalyzing the degradation of polyethylene, and can make the distribution of the prepared liquid product more concentrated, thereby increasing the added value.

[0012] Preferably, the acidic molecular sieve is prepared by the following method:

[0013] The EMT / FAU eutectic molecular sieve and an inorganic ammonium salt solution are ion exchanged at 75°C to 95°C to introduce ammonium ions. After filtering and drying, the mixture is calcined at 350°C to 550°C to convert the ammonium ions into acidic sites to obtain an acidic molecular sieve.

[0014] Preferably, the pH of the acidic molecular sieve is 6-7; the mass ratio of the EMT / FAU eutectic molecular sieve and the inorganic ammonium salt solution is 5-11:33; the inorganic ammonium salt solution is obtained by mixing an inorganic ammonium salt and water in a mass ratio of 1-4:11; and the inorganic ammonium salt is ammonium chloride or ammonium sulfate.

[0015] Further preferably, the EMT / FAU eutectic molecular sieve is prepared by the following method:

[0016] Sodium hydroxide, water, an Al source, sodium phosphate, 18-crown ether-6 and silica sol are stirred and mixed to obtain a mixed solution; the mixed solution is aged and crystallized, filtered, dried, and then calcined at 350° C. to 550° C. to obtain an EMT / FAU eutectic molecular sieve.

[0017] Preferably, the Al source is sodium metaaluminate; the mass of silicon particles in the silica sol accounts for 25% of the total mass of the silica sol; the mass ratio of sodium hydroxide, Al source, sodium phosphate, 18-crown ether-6 and silica sol is 0.4-0.42:1:0.03:0.55:10.

[0018] The present invention can adjust the ratio of the two-phase molecular sieve by adjusting the ratio of NaOH to prepare the EMT / FAU eutectic molecular sieve, which has better polyethylene cracking catalytic performance than single EMT or FAU molecular sieves.

[0019] The EMT / FAU eutectic molecular sieve of the present invention combines EMT and FAU topologies. The two pore structures formed by the six-membered rings in the β cage facilitate the diffusion of large polyethylene molecules. The Si / Al ratio is 5 to 15, and a higher Si / Al ratio increases the acidity of the EMT / FAU eutectic molecular sieve. The present invention also uses ammonium ion exchange to increase Brønsted acid sites, further facilitating the cracking and isomerization of polyethylene.

[0020] Preferably, the Pt-loaded TS-1 molecular sieve is prepared by the following method:

[0021] A silicon source, a titanium source and tetrapropylammonium hydroxide are stirred and mixed in an ice-water bath, and then stirred and reacted in an alcohol aqueous solution at 50°C to 90°C to obtain a first solution; H2PtCl6 is used as a platinum precursor, and the H2PtCl6 solution and 3-mercaptopropyltrimethoxysilane solution are stirred and mixed to obtain a second solution containing a Pt precursor; the first solution and the second solution containing the Pt precursor are mixed and reacted at 50°C to 90°C, and then crystallized at 120°C to 250°C, filtered and dried, and then calcined at 300°C to 600°C to obtain a Pt-loaded TS-1 molecular sieve.

[0022] The Pt-loaded TS-1 molecular sieve of the present invention can provide abundant metal hydrogenation sites, thereby enabling olefin intermediates to undergo rapid diffusion hydrogenation to generate short-chain liquid alkanes.

[0023] Preferably, the silicon source is ethyl orthosilicate; the titanium source is tetrabutyl titanate; the alcohol aqueous solution is an isopropyl alcohol aqueous solution; and the mass ratio of the silicon source, the titanium source and tetrapropylammonium hydroxide is 40:1-5:10-20.

[0024] Preferably, the 3-mercaptopropyltrimethoxysilane solution is obtained by mixing 3-mercaptopropyltrimethoxysilane, sodium hydroxide and water; the mass ratio of 3-mercaptopropyltrimethoxysilane, sodium hydroxide and water is 0.12:0.05~0.2:1~10; the amount ratio of H2PtCl6 to 3-mercaptopropyltrimethoxysilane is 0.616mmol:0.05~0.2g.

[0025] The second aspect of the present invention provides a method for preparing the EMT / FAU eutectic molecular sieve catalyst according to the first aspect, comprising the following steps:

[0026] The EMT / FAU eutectic molecular sieve is ion exchanged in an inorganic ammonium salt solution to introduce ammonium ions to increase Brønsted acid sites, and then dried and calcined to obtain an acidic molecular sieve. The acidic molecular sieve and Pt-loaded TS-1 molecular sieve are physically mixed to obtain an EMT / FAU eutectic molecular sieve catalyst.

[0027] The third aspect of the present invention provides an application of an EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking, and the specific application method is as follows:

[0028] In a hydrogen atmosphere with a hydrogen pressure of 0.5 MPa to 4 MPa, waste polyolefins and EMT / FAU eutectic molecular sieve catalysts are stirred and reacted at 220° C. to 260° C., and after the reaction, hydrogenation cracking products are collected; the mass ratio of the waste polyolefins to the EMT / FAU eutectic molecular sieve catalysts is 1 to 3:0.2.

[0029] The present invention utilizes acidic molecular sieves to provide acidic sites, causing polyethylene to undergo a preliminary reaction to generate olefin intermediates. Utilizing metal sites provided by Pt-loaded TS-1 molecular sieves, the olefin intermediates are further hydrogenated at the metal sites provided by the Pt-loaded TS-1 molecular sieves to generate liquid alkanes. This tandem reaction greatly reduces reaction time, improves the activity of the EMT / FAU eutectic molecular sieve catalyst, and can convert polyethylene into the target product under mild conditions.

[0030] Beneficial effects of the present invention:

[0031] 1. The present invention obtains an acidic molecular sieve by exchanging ammonium ions on the EMT / FAU eutectic molecular sieve to increase Brønsted acid sites; uses TS-1 molecular sieve to encapsulate Pt to provide abundant metal hydrogenation sites; and constructs an acidic site-metal series system by combining the acidic molecular sieve with the Pt-loaded TS-1 molecular sieve. This system can convert polyethylene into short-chain alkanes under mild conditions, making the distribution of liquid products more concentrated. This solves the problems of existing molecular sieve catalysts in polyethylene hydrocracking reactions, such as excessively high hydrogen pressure, high energy consumption, and non-concentrated distribution of reaction products.

[0032] 2. The EMT / FAU eutectic molecular sieve catalyst of the present invention can improve catalytic activity and reduce hydrogen pressure in the polyethylene hydrocracking reaction, while efficiently catalyzing polyethylene degradation and making the prepared liquid product more concentrated, thereby increasing added value.

[0033] 3. The present invention can improve the coke resistance of EMT / FAU eutectic molecular sieve catalysts, help design efficient waste plastic value-added catalysts, and explore new methods for environmental protection and resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a scanning electron microscope image of the EMT / FAU eutectic molecular sieve of Example 1.

[0035] Figure 2 This is a scanning electron microscope image of the EMT / FAU eutectic molecular sieve of Example 2.

[0036] Figure 3 The X-ray diffraction patterns of the EMT / FAU eutectic molecular sieves of Examples 1 and 2 are shown.

[0037] Figure 4 This is a transmission electron microscope image of the Pt@TS-1 molecular sieve in Example 1.

[0038] Figure 5 This is the product distribution diagram of the hydrocracking polyethylene of Application Example 1.

[0039] Figure 6This is the product distribution diagram of the hydrocracking polyethylene of Application Example 2. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0042] In the following embodiments, EMT and FAU represent two different types of molecular sieve structures, respectively. The full name of EMT in English is Extended Molecular Template, and its Chinese name is Ettite molecular sieve. The full name of FAU molecular sieve in English is Faujasite Molecular Sieve, and its Chinese name is analcime molecular sieve.

[0043] In the following examples, TS-1 is a titanium silicate molecular sieve, which belongs to the Pentasil type heteroatom molecular sieve. The Pt-loaded TS-1 molecular sieve is denoted as Pt@TS-1 molecular sieve.

[0044] In the process of synthesizing the EMT / FAU eutectic molecular sieve of the present invention, the ratio of the two-phase molecular sieve can be adjusted by adjusting the NaOH ratio. When the amount of NaOH is appropriately reduced, it is helpful to form an EMT / FAU eutectic molecular sieve with an EMT structure as the main component; when the amount of NaOH is appropriately increased, it is helpful to form an EMT / FAU eutectic molecular sieve with a FAU structure as the main component.

[0045] The EMT / FAU eutectic molecular sieve synthesized using 18-crown-6 as a structure-directing agent has high crystallinity and purity, and better thermal stability. The invention can reduce crystallization time by introducing a phosphide.

[0046] The present invention increases Brønsted acid sites by exchanging ammonium ions on the EMT / FAU eutectic molecular sieve, allowing polyethylene to initially react to form olefin intermediates. The olefin intermediates are further hydrogenated at the metal sites provided by the Pt@TS-1 molecular sieve to form liquid alkanes. This acid site-metal tandem reaction greatly reduces reaction time, improves the activity of the EMT / FAU eutectic molecular sieve catalyst, and can convert polyethylene into the target product under mild conditions.

[0047] The controllably synthesized acidic molecular sieve of this invention contains numerous acidic sites. When used in tandem with Pt@TS-1 molecular sieve to catalyze polyethylene production, it achieves higher reaction rates and liquid fuel yields, with a more concentrated distribution of liquid products. The EMT / FAU eutectic molecular sieve catalyst prepared in this invention exhibits improved stability and achieves efficient and selective degradation of polyolefin plastics under relatively mild reaction conditions. Its universal applicability suggests a new approach to environmental protection and resource recovery.

[0048] The technical solution of the present invention is further described below through specific embodiments.

[0049] In the following examples, the methods described are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0050] The room temperature is 25°C. The temperature of the ice water bath is between 0°C and 5°C.

[0051] The mass of silicon particles in the silica sol accounts for 25% of the total mass of the silica sol.

[0052] Example 1

[0053] A method for preparing an EMT / FAU eutectic molecular sieve catalyst comprises the following steps:

[0054] Step 1, preparation of EMT / FAU eutectic molecular sieve:

[0055] 0.4 g of sodium hydroxide, 3.7 g of water, 1 g of sodium metaaluminate, 0.03 g of sodium phosphate, 0.55 g of 18-crown ether-6 and 10 g of silica sol were stirred at room temperature for 2 h to obtain a mixed solution.

[0056] The mixed solution was aged at 23°C for 24 hours; the aged sol was transferred to a 25 mL crystallization kettle and crystallized at 100°C for 6 days; after crystallization, it was cooled to room temperature, filtered, washed, and dried at 60°C for 24 hours, then placed in a muffle furnace, heated to 550°C at a heating rate of 5°C / min, and calcined at this temperature for 8 hours to remove the structure-directing agent 18-crown ether-6 to obtain the EMT / FAU eutectic molecular sieve.

[0057] Step 2, preparation of acidic molecular sieve:

[0058] EMT / FAU eutectic molecular sieve, ammonium chloride and water were weighed according to a mass ratio of EMT / FAU eutectic molecular sieve, ammonium chloride and water of 1:3:30; ammonium chloride was dissolved in water, and then EMT / FAU eutectic molecular sieve was added, and the mixture was treated in a 90°C water bath for 1.5 hours to exchange the EMT / FAU eutectic molecular sieve with ammonia, filtered, dried at 60°C for 24 hours, and then placed in a muffle furnace, heated to 550°C at a heating rate of 3°C / min, and calcined at this temperature for 6 hours to obtain an acidic molecular sieve with a pH of 6 to 7.

[0059] Step 3, preparation of Pt-loaded TS-1 molecular sieve:

[0060] 40 g of ethyl orthosilicate, 2.64 g of tetrabutyl titanate, and 56.72 g of 25 wt% tetrapropylammonium hydroxide were stirred and mixed in an ice-water bath for 1 hour; then, the mixture was steamed open in a 70°C water bath for 30 minutes, and 30 g of water was added, and the mixture was stirred and mixed for 2.5 hours; 48 g of isopropyl alcohol was added, and the mixture was stirred for 1 hour to obtain a first solution.

[0061] 0.10 g of sodium hydroxide, 2.0 g of water and 0.12 g of 3-mercaptopropyltrimethoxysilane were stirred and mixed for 20 minutes, and then 6.16 mL of 100 mM H2PtCl6 was added dropwise, and stirring was continued for 20 minutes to obtain a second solution.

[0062] The second solution was slowly added dropwise to the first solution, and the mixture was stirred in a water bath at 70°C for 30 min. The mixture was then transferred to a crystallization kettle and crystallized at 170°C for 24 h. After the crystallization was completed, the mixture was cooled to room temperature, filtered, washed, and dried at 60°C for 24 h. The mixture was then placed in a muffle furnace and calcined at 550°C for 4 h to obtain Pt-loaded TS-1 molecular sieve, which was designated as Pt@TS-1 molecular sieve.

[0063] Step 4, preparation of EMT / FAU eutectic molecular sieve catalyst:

[0064] The acidic molecular sieve and Pt@TS-1 molecular sieve were stirred and mixed in a mass ratio of 1:1 to obtain an EMT / FAU eutectic molecular sieve catalyst.

[0065] Example 2

[0066] A method for preparing an EMT / FAU eutectic molecular sieve catalyst comprises the following steps:

[0067] Step 1, preparation of EMT / FAU eutectic molecular sieve:

[0068] 0.42 g of sodium hydroxide, 3.7 g of water, 1 g of sodium metaaluminate, 0.03 g of sodium phosphate, 0.55 g of 18-crown ether-6 and 10 g of silica sol were stirred at room temperature for 2 h to obtain a mixed solution.

[0069] The mixed solution was aged at 23°C for 24 hours; the aged sol was transferred to a 25 mL crystallization kettle and crystallized at 100°C for 6 days; after crystallization, it was cooled to room temperature, filtered, washed, and dried at 60°C for 24 hours, then placed in a muffle furnace, heated to 550°C at a heating rate of 5°C / min, and calcined at this temperature for 8 hours to remove the structure-directing agent 18-crown ether-6 to obtain the EMT / FAU eutectic molecular sieve.

[0070] Step 2, preparation of acidic molecular sieve:

[0071] EMT / FAU eutectic molecular sieve, ammonium chloride and water were weighed according to a mass ratio of EMT / FAU eutectic molecular sieve, ammonium chloride and water of 1:3:30; ammonium chloride was dissolved in water, and then EMT / FAU eutectic molecular sieve was added, and the mixture was treated in a 90°C water bath for 1.5 hours to exchange the EMT / FAU eutectic molecular sieve with ammonia, filtered, dried at 60°C for 24 hours, and then placed in a muffle furnace, heated to 550°C at a heating rate of 3°C / min, and calcined at this temperature for 6 hours to obtain an acidic molecular sieve with a pH of 6 to 7.

[0072] Step 3, preparation of Pt-loaded TS-1 molecular sieve:

[0073] 40 g of ethyl orthosilicate, 2.64 g of tetrabutyl titanate, and 56.72 g of 25 wt% tetrapropylammonium hydroxide were stirred and mixed in an ice-water bath for 1 hour; then, the mixture was steamed open in a 70°C water bath for 30 minutes, and 30 g of water was added, and the mixture was stirred and mixed for 2.5 hours; 48 g of isopropyl alcohol was added, and the mixture was stirred for 1 hour to obtain a first solution.

[0074] 0.10 g of sodium hydroxide, 2.0 g of water and 0.12 g of 3-mercaptopropyltrimethoxysilane were stirred and mixed for 20 minutes, and then 6.16 mL of a 100 mM H2PtCl6 solution was added dropwise, and stirring was continued for 20 minutes to obtain a second solution.

[0075] The second solution was slowly added dropwise to the first solution, and the mixture was stirred in a water bath at 70°C for 30 min. The mixture was then transferred to a crystallization kettle and crystallized at 170°C for 24 h. After the crystallization was completed, the mixture was cooled to room temperature, filtered, washed, and dried at 60°C for 24 h. The mixture was then placed in a muffle furnace and calcined at 550°C for 4 h to obtain Pt-loaded TS-1 molecular sieve, which was designated as Pt@TS-1 molecular sieve.

[0076] Step 4, preparation of EMT / FAU eutectic molecular sieve catalyst:

[0077] The acidic molecular sieve and Pt@TS-1 molecular sieve were stirred and mixed in a mass ratio of 1:1 to obtain an EMT / FAU eutectic molecular sieve catalyst.

[0078] Test 1: Scanning electron microscopy and X-ray diffraction analysis.

[0079] The EMT / FAU eutectic molecular sieves prepared in Example 1 and Example 2 were analyzed by scanning electron microscopy. Figure 1 and Figure 2 shown.

[0080] Depend on Figure 1 and Figure 2 It can be seen that a small amount of FAU molecular sieve particles grow on the EMT molecular sieve. By slightly increasing the NaOH content, the proportion of FAU molecular sieve in the EMT / FAU eutectic molecular sieve increases, and the crystals show a high degree of twinning.

[0081] The EMT / FAU eutectic molecular sieves prepared in Example 1 and Example 2 were subjected to X-ray diffraction analysis. The results are as follows: Figure 3 shown.

[0082] Depend on Figure 3 It can be seen that three peaks appear in the range of 5°≤2θ≤7°, which are the 100, 002 and 101 reflections of the hexagonal EMT molecular sieve. The 002 reflection position of the EMT molecular sieve coincides with the 111 reflection position of the cubic FAU molecular sieve. With the increase of NaOH, the FAU crystal form tends to be generated.

[0083] From the above analysis, it can be seen that a slight increase in the NaOH content directly results in an increase in the particle size of the FAU molecular sieve on the surface, and by comparing the characteristic peaks of X-ray diffraction, it can be seen that the reflection peak of 002 in Example 2 is more prominent.

[0084] The Pt@TS-1 molecular sieve of Example 1 was analyzed by transmission electron microscopy. Figure 4 shown.

[0085] Depend on Figure 4 It can be seen that the Pt@TS-1 molecular sieve has a cubic shape and high crystallinity, which is consistent with the characteristic structure of the molecular sieve. Pt does not show obvious agglomeration, that is, there are no obvious metal clusters larger than 10nm, and is evenly encapsulated inside the TS-1 molecular sieve.

[0086] Next, polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic molecular sieve catalyst prepared in Examples 1 and 2 above.

[0087] Application Example 1

[0088] The polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic molecular sieve catalyst prepared in Example 1. The specific method includes the following steps:

[0089] 1g of low-density polyethylene (LDPE) with a melt index of 20g-30g / 10min and a particle size of ~1000 mesh and 0.2g of EMT / FAU eutectic molecular sieve catalyst were added to an autoclave, stirred and mixed thoroughly, and reacted at 260°C under 2MPa of H₂ for 1 hour. After the autoclave cooled to room temperature, the remaining H₂ and a small amount of gaseous alkanes were collected and extracted with dichloromethane to separate the remaining solid and liquid products. The extract and solid product were then separated by filtration. The collected extract contained the liquid product of the reaction, and the liquid product and collected gas were analyzed by gas chromatography. The liquid product was liquid alkane, with a yield of 91.3%, including 86.5% selectivity for C5-C9 hydrocarbons. The gas yield was 5.4%.

[0090] Application Example 2

[0091] The polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic molecular sieve catalyst prepared in Example 2. The specific method includes the following steps:

[0092] 1g of low-density polyethylene (LDPE) with a melt index of 20g-30g / 10min and a particle size of ~1000 mesh and 0.2g of EMT / FAU eutectic molecular sieve catalyst were added to an autoclave, stirred and mixed thoroughly, and reacted at 260°C under 2 MPa of H₂ for 1 hour. After the autoclave cooled to room temperature, the remaining H₂ and a small amount of gaseous alkanes were collected and extracted with dichloromethane to separate the remaining solid and liquid products. The extract and solid product were then separated by filtration. The collected extract contained the liquid product of the reaction, and the liquid product and collected gas were analyzed by gas chromatography. The liquid product was liquid alkane, with a yield of 93.1%, and the selectivity for C5-C9 hydrocarbons reached 88.5%. The gas yield was 6.2%.

[0093] Application Example 3

[0094] A polyethylene hydrocracking reaction was performed using the EMT / FAU eutectic molecular sieve catalyst prepared in Example 1. A first polyethylene hydrocracking reaction was performed according to the method of Application Example 1. The liquid product of the first polyethylene hydrocracking reaction and the EMT / FAU eutectic molecular sieve catalyst were collected and separated. The polyethylene hydrocracking reaction was repeated five times using 0.2 g of the separated EMT / FAU eutectic molecular sieve catalyst and 1 g of low-density polyethylene having a melt index of 20 g to 30 g / 10 min and a particle size of 1000 mesh according to the method of Application Example 1. The liquid products and collected gases after the five reaction cycles were analyzed by gas chromatography.

[0095] Application Example 4

[0096] The polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic molecular sieve catalyst prepared in Example 1. The polyethylene hydrocracking reaction was carried out according to the method of Application Example 1, except that the low-density polyethylene with a melt index of 20g~30g / 10min and a particle size of 1000 mesh was replaced with high-density polyethylene balls.

[0097] Application Example 5

[0098] The polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic molecular sieve catalyst prepared in Example 1. The polyethylene hydrocracking reaction was carried out according to the method of Application Example 1, except that the low-density polyethylene with a melt index of 20g~30g / 10min and a particle size of 1000 mesh was replaced by high-density polypropylene.

[0099] Test 2: Hydrocracking Polyethylene Product Analysis.

[0100] The EMT / FAU eutectic molecular sieve catalysts prepared in Example 1 and Example 2 were subjected to polyethylene hydrocracking reaction, and the collected hydrocracking polyethylene products were analyzed by gas chromatography. The results are as follows: Figure 5 and Figure 6 At the same time, the liquid product and the collected gas after 5 cycles of reaction in Application Example 3 were subjected to gas chromatography analysis; the hydrocracking polyethylene products collected in Application Example 4 and Application Example 5 were subjected to gas chromatography analysis; the results are shown in Table 1.

[0101] Table 1 Yields of liquid products and gases

[0102]

[0103] Combined with Table 1 Figure 5 and Figure 6 It can be seen that in Application Examples 1 to 5, the liquid products are concentrated in C5 to C9 hydrocarbons, with a higher liquid fuel yield. The series application of eutectic molecular sieve and Pt@TS-1 improves the hydrocracking rate and realizes the shift of the distribution of polyolefin catalytic products to narrowly distributed oil alkanes.

[0104] In Application Example 3, after 5 cycles of reaction, the liquid product still reached 84.6%, and the selectivity of C5-C9 hydrocarbons reached 85.9%, which shows that the EMT / FAU eutectic molecular sieve catalyst prepared in this embodiment of the present invention has relatively good stability.

[0105] The results of Application Example 1, Application Example 4 and Application Example 5 show that the EMT / FAU eutectic molecular sieve catalyst prepared in the embodiment of the present invention has high activity and high yield of liquid products for polyolefin raw materials such as low-density polyethylene, high-density polyethylene balls and high-density polypropylene, showing good universality.

[0106] From the above analysis, it can be seen that the controllably synthesized acidic molecular sieves of the present invention contain a large number of acidic sites. When used in tandem with Pt@TS-1 molecular sieves to catalyze polyethylene, they can achieve higher reaction rates and liquid fuel yields, with a more concentrated distribution of liquid products. The EMT / FAU eutectic molecular sieve catalyst prepared in this embodiment of the present invention exhibits relatively good stability and can achieve efficient and selective degradation of polyolefin plastics under relatively mild reaction conditions. This catalyst has universal applicability and explores new avenues for environmental protection and resource recovery.

[0107] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of an EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking, characterized in that: The specific application methods are as follows: In a hydrogen atmosphere with a hydrogen pressure of 0.5 MPa to 4 MPa, waste polyolefins and EMT / FAU eutectic molecular sieve catalyst are stirred and reacted at 220°C to 260°C. After the reaction, the hydrocracking products are collected. Among the hydrocracking products, the liquid products are mainly distributed in C5 to C9 hydrocarbons. The mass ratio of waste polyolefin and EMT / FAU eutectic molecular sieve catalyst is 1-3:0.2; The EMT / FAU eutectic molecular sieve catalyst is obtained by physically mixing an acidic molecular sieve and a Pt-loaded TS-1 molecular sieve, and an acidic site-metal series system is constructed by the acidic molecular sieve and the Pt-loaded TS-1 molecular sieve; wherein the mass ratio of the acidic molecular sieve to the Pt-loaded TS-1 molecular sieve is 1:1; The acidic molecular sieve is prepared by subjecting the EMT / FAU eutectic molecular sieve to ion exchange in an inorganic ammonium salt solution to introduce ammonium ions to increase Brønsted acid sites, followed by drying and calcination to obtain the acidic molecular sieve. The mass ratio of EMT / FAU eutectic molecular sieve to inorganic ammonium salt solution is 5-11:33; the inorganic ammonium salt solution is obtained by mixing inorganic ammonium salt and water in a mass ratio of 1-4:11; The Pt-loaded TS-1 molecular sieve is prepared by the following method: Stirring and mixing a silicon source, a titanium source, and tetrapropylammonium hydroxide in an ice-water bath, and then stirring and reacting them in an alcohol aqueous solution at 50° C. to 90° C. to obtain a first solution; Using H2PtCl6 as a platinum precursor, stirring and mixing the H2PtCl6 solution and the 3-mercaptopropyltrimethoxysilane solution to obtain a second solution containing a Pt precursor; The first solution and the second solution containing the Pt precursor are mixed and reacted at 50°C to 90°C, then crystallized at 120°C to 250°C, filtered and dried, and then calcined at 300°C to 600°C to obtain the Pt-loaded TS-1 molecular sieve.

2. The use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 1, characterized in that: The acidic molecular sieve is prepared by the following method: The EMT / FAU eutectic molecular sieve and an inorganic ammonium salt solution are ion exchanged at 75°C to 95°C to introduce ammonium ions. After filtering and drying, the mixture is calcined at 350°C to 550°C to convert the ammonium ions into acidic sites to obtain an acidic molecular sieve.

3. Use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 2, characterized in that: The pH of the acidic molecular sieve is 6-7; the inorganic ammonium salt is ammonium chloride or ammonium sulfate.

4. Use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 1, characterized in that: The silicon source is tetraethyl orthosilicate; the titanium source is tetrabutyl titanate; and the alcohol aqueous solution is an isopropyl alcohol aqueous solution; The mass ratio of the silicon source, the titanium source and tetrapropylammonium hydroxide is 40:1-5:10-20.

5. Use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 1, characterized in that: The 3-mercaptopropyltrimethoxysilane solution is prepared by mixing 3-mercaptopropyltrimethoxysilane, sodium hydroxide and water; The mass ratio of 3-mercaptopropyltrimethoxysilane, sodium hydroxide and water is 0.12:0.05-0.2:1-10; The usage ratio of H2PtCl6 to 3-mercaptopropyltrimethoxysilane is 0.616mmol:0.05~0.2g.

6. Use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 1, characterized in that: The EMT / FAU eutectic molecular sieve is prepared by the following method: Sodium hydroxide, water, an Al source, sodium phosphate, 18-crown ether-6 and silica sol are stirred and mixed to obtain a mixed solution; the mixed solution is aged and crystallized, filtered, dried and then calcined to obtain an EMT / FAU eutectic molecular sieve.

7. Use of the EMT / FAU eutectic molecular sieve catalyst in polyolefin hydrocracking according to claim 6, characterized in that: The Al source is sodium metaaluminate; the mass of silicon particles in the silica sol accounts for 25% of the total mass of the silica sol; The mass ratio of sodium hydroxide, Al source, sodium phosphate, 18-crown ether-6 and silica sol is 0.4-0.42:1:0.03:0.55:10.

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