EMT / FAU eutectic molecular sieve catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of polyolefin degradation, in particular to an EMT / FAU eutectic molecular sieve catalyst and a preparation method and application thereof. 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 the mass ratio of the acidic molecular sieve to the Pt-loaded TS-1 molecular sieve is 1: 1. The method comprises the following steps: carrying out ammonium ion exchange on an EMT / FAU eutectic molecular sieve to obtain an acidic molecular sieve; pt is packaged by using a TS-1 molecular sieve so as to provide abundant metal hydrogenation sites; an acid site-metal series system is constructed through an acid molecular sieve and a Pt-loaded TS-1 molecular sieve, polyethylene can be converted into short-chain alkane under a mild condition, liquid products are distributed more intensively, and the problems that an existing molecular sieve catalyst is too high in hydrogen pressure in a polyethylene hydrocracking reaction, and the reaction time is shortened are solved. The energy consumption is high; and reaction products are not distributed intensively.

Description

Technical Field

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

[0002] As one of the largest consumption categories of plastics, polyolefins are widely used in fields such as packaging, construction, and medical and health. Due to the non-degradability of polyolefins, serious environmental problems have been caused. Currently, most plastic wastes are treated by landfilling or incineration, which not only generates greenhouse gases but also causes environmental pollution. And converting plastic wastes into the original plastics through mechanical recycling usually leads to the degradation of their physical and mechanical properties and reduces their value. In recent years, chemical catalytic conversion has become a promising solution, which can efficiently convert plastic wastes into high-purity and high-value-added chemicals, such as liquid fuels and naphtha, etc., to promote the development of the circular economy.

[0003] Research shows that the catalytic hydrocracking of polyolefins can effectively cleave the long chains of polyethylene through bifunctional catalysts, such as zeolite and metal composite systems. For example, the process of catalytic hydrocracking of polyethylene includes: polyethylene adsorbs onto metal sites, the metal sites dehydrogenate to generate olefin intermediates; the olefin intermediates desorb and diffuse to Brønsted acid sites to be converted into carbocation reaction intermediates; the carbocation reaction intermediates then undergo isomerization and β-cleavage, and subsequently diffuse back to the metal sites to be hydrogenated into linear and branched alkanes. Among them, Brønsted acid sites are usually called Bronsted acid sites, which can release protons to participate in catalytic reactions in porous materials such as zeolites.

[0004] Currently, zeolite catalysts are widely used in the catalytic decomposition of polyethylene due to their unique topological structures. For example, in the prior art 1: Brandon C. Vance et al. published a paper in the 487th issue of the Journal of Chemical Engineering in 2024, and the paper number is 150468. This study developed a Ni / Beta catalyst for polyolefin hydrocracking. In this study, the researchers loaded metal Ni on Beta zeolite to achieve the catalytic hydrocracking of polyethylene. Under the conditions of 250 °C and 6 Mpa H2, the complete decomposition of low-density polyethylene was achieved within 12 hours. However, the reaction conditions for using this Ni / Beta catalyst for polyolefin hydrocracking are relatively harsh, with too high H2 pressure, which not only increases the danger but also raises the production cost, and requires a long reaction time.

[0005] Prior Art 2: CN119215967A discloses a micro - metal / molecular sieve catalyst. By mechanically ball - milling to modify traditional microporous molecular sieves and loading micro - metals thereon, the accessibility of long - chain alkane molecules of waste polyolefins to the loaded metal particles and the acidic sites of the molecular sieve is improved, so as to achieve the promotion of the maximum conversion of polyolefins into isomeric fuels while saving the metal loading amount. However, when using this micro - metal / molecular sieve catalyst to catalytically degrade waste polyolefins at low temperature to prepare isomeric fuels, the resulting product distribution is wide, 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] To solve the above - mentioned technical problems, the present invention provides an EMT / FAU eutectic molecular sieve catalyst, a preparation method thereof, and an application.

[0007] The present invention designs an EMT / FAU eutectic molecular sieve catalyst that requires a low hydrogen pressure, has a concentrated liquid product distribution, high added value, and is highly efficient in catalytically degrading waste polyolefins. It can effectively decompose waste polyolefin plastics, has universality, and solves the problems of too high hydrogen pressure, large energy consumption, and non - concentrated reaction product distribution in the polyethylene hydrocracking reaction of existing molecular sieve catalysts.

[0008] To achieve the above object, the technical solution of the present invention is as follows.

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

[0010] The present invention performs ammonium ion exchange on the EMT / FAU eutectic molecular sieve to increase Brønsted acid sites to obtain an acidic molecular sieve; encapsulates Pt with the TS - 1 molecular sieve to provide abundant metal hydrogenation sites; constructs an acidic site - metal tandem system through the acidic molecular sieve and the TS - 1 molecular sieve loaded with Pt, which can convert polyethylene into short - chain alkanes under mild conditions, making the liquid product distribution more concentrated, and solving the problems of too high hydrogen pressure, large energy consumption, and non - concentrated reaction product distribution in the polyethylene hydrocracking reaction of existing molecular sieve catalysts.

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

[0012] Preferably, the acidic zeolite is prepared by the following method: The EMT / FAU eutectic zeolite and the inorganic ammonium salt solution are subjected to ion exchange at 75 °C to 95 °C to introduce ammonium ions. After filtration and drying, calcination is carried out at 350 °C to 550 °C to convert the ammonium ions into acidic sites, thereby obtaining the acidic zeolite.

[0013] Preferably, the pH of the acidic zeolite is 6 to 7; the mass ratio of the EMT / FAU eutectic zeolite to the inorganic ammonium salt solution is 5 to 11:33; the inorganic ammonium salt solution is obtained by mixing an inorganic ammonium salt and water in a mass ratio of 1 to 4:11; the inorganic ammonium salt is ammonium chloride or ammonium sulfate.

[0014] More preferably, the EMT / FAU eutectic zeolite is prepared by the following method: Sodium hydroxide, water, an Al source, sodium phosphate, 18-crown-6, and silica sol are stirred and mixed to obtain a mixed solution; the mixed solution is aged and crystallized, filtered and dried, and then calcined at 350 °C to 550 °C to obtain the EMT / FAU eutectic zeolite.

[0015] Preferably, the Al source is sodium aluminate; 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, the Al source, sodium phosphate, 18-crown-6, and silica sol is 0.4 to 0.42:1:0.03:0.55:10.

[0016] By adjusting the proportion of NaOH, the present invention can adjust the proportion of the two-phase zeolite and prepare the EMT / FAU eutectic zeolite, which has better catalytic performance for polyethylene cracking compared with the single EMT or FAU zeolite prepared.

[0017] The EMT / FAU eutectic zeolite of the present invention combines the EMT and FAU topological structures. Among them, the two pore structures formed by the β cages linked through six-membered rings are beneficial to the diffusion of macromolecular polyethylene; and the Si / Al ratio is 5 to 15, and the higher Si / Al ratio increases the acidity of the EMT / FAU eutectic zeolite. The present invention also increases the Brønsted acid sites by performing ammonium ion exchange on the EMT / FAU eutectic zeolite, which is more beneficial to the cracking and isomerization of polyethylene.

[0018] Preferably, the Pt-loaded TS-1 zeolite is prepared by the following method: Mix the silicon source, titanium source and tetrapropylammonium hydroxide under an ice-water bath, and then stir and react in an aqueous alcohol solution at 50 °C to 90 °C to obtain a first solution; use H2PtCl6 as the platinum precursor, stir and mix the H2PtCl6 solution and 3-mercaptopropyltrimethoxysilane solution to obtain a second solution containing the Pt precursor; mix and react the first solution with the second solution containing the Pt precursor at 50 °C to 90 °C, and then carry out crystallization treatment at 120 °C to 250 °C. After filtration and drying, calcine at 300 °C to 600 °C to obtain the Pt-loaded TS-1 molecular sieve.

[0019] The Pt-loaded TS-1 molecular sieve of the present invention can provide abundant metal hydrogenation sites, so that olefin intermediates can be quickly hydrogenated by diffusion to generate short-chain liquid alkanes.

[0020] Preferably, the silicon source is tetraethyl orthosilicate; the titanium source is tetrabutyl titanate; the aqueous alcohol solution is an aqueous isopropanol solution; the mass ratio of the silicon source, titanium source and tetrapropylammonium hydroxide is 40:1 to 5:10 to 20.

[0021] 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 to 0.2:1 to 10; the dosage ratio of H2PtCl6 to 3-mercaptopropyltrimethoxysilane is 0.616 mmol:0.05 to 0.2 g.

[0022] The second aspect of the present invention provides a preparation method of the EMT / FAU eutectic molecular sieve catalyst described in the first aspect, including the following steps: Perform ion exchange on the EMT / FAU eutectic molecular sieve in an inorganic ammonium salt solution to introduce ammonium ions to increase Brønsted acid sites, and perform calcination after drying to obtain an acidic molecular sieve; physically mix the acidic molecular sieve and the Pt-loaded TS-1 molecular sieve to obtain the EMT / FAU eutectic molecular sieve catalyst.

[0023] The third aspect of the present invention provides an application of the EMT / FAU eutectic molecular sieve catalyst in the hydrocracking of polyolefins. The specific application method is as follows: In a hydrogen atmosphere with a hydrogen pressure of 0.5 Mpa to 4 Mpa, stir and react the waste polyolefin and the EMT / FAU eutectic molecular sieve catalyst at 220 °C to 260 °C, and collect the hydrocracking products after the reaction; the mass ratio of the waste polyolefin to the EMT / FAU eutectic molecular sieve catalyst is 1 to 3:0.2.

[0024] The present invention utilizes an acidic molecular sieve to provide acidic sites, enabling polyethylene to undergo a preliminary reaction to form olefin intermediates; and utilizes the metal sites provided by TS-1 molecular sieve loaded with Pt, where the olefin intermediates further undergo hydrogenation at the metal sites provided by the TS-1 molecular sieve loaded with Pt to form liquid alkanes. This tandem reaction mode greatly reduces the reaction time, improves the activity of the EMT / FAU eutectic molecular sieve catalyst, and can convert polyethylene into the target product under mild conditions.

[0025] Advantages of the present invention: 1. By performing ammonium ion exchange on the EMT / FAU eutectic molecular sieve, the present invention increases the Brønsted acid sites to obtain an acidic molecular sieve; encapsulates Pt using the TS-1 molecular sieve to provide abundant metal hydrogenation sites; constructs an acidic site-metal tandem system through the acidic molecular sieve and the TS-1 molecular sieve loaded with Pt, which can convert polyethylene into short-chain alkanes under mild conditions, making the liquid product distribution more concentrated, and solving the problems of high hydrogen pressure, large energy consumption, and non-concentrated reaction product distribution in the polyethylene hydrocracking reaction of existing molecular sieve catalysts.

[0026] 2. The EMT / FAU eutectic molecular sieve catalyst of the present invention can improve the catalytic activity, reduce the hydrogen pressure in the polyethylene hydrocracking reaction, efficiently catalyze the degradation of polyethylene, and make the prepared liquid product distribution more concentrated, thereby increasing the added value.

[0027] 3. The present invention can improve the coke resistance of the EMT / FAU eutectic molecular sieve catalyst, contribute to the design of highly efficient waste plastic value-added catalysts, and explore new methods for environmental protection and resource recycling. Description of the Drawings

[0028] Figure 1 It is the scanning electron microscope image of the EMT / FAU eutectic molecular sieve of Example 1.

[0029] Figure 2 It is the scanning electron microscope image of the EMT / FAU eutectic molecular sieve of Example 2.

[0030] Figure 3 It is the X-ray diffraction pattern of the EMT / FAU eutectic molecular sieve of Example 1 and Example 2.

[0031] Figure 4 It is the transmission electron microscope image of the Pt@TS-1 molecular sieve in Example 1.

[0032] Figure 5 It is the product distribution diagram of the hydrocracked polyethylene of Application Example 1.

[0033] Figure 6 It is the product distribution diagram of the hydrocracked polyethylene of Application Example 2. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0036] In the following embodiments, EMT and FAU respectively represent two different types of molecular sieve structures. The full English name of EMT is Extended Molecular Template, and the Chinese name is ETS-10 molecular sieve. The English name of FAU molecular sieve is Faujasite Molecular Sieve, and the Chinese name is Faujasite molecular sieve.

[0037] In the following embodiments, TS-1 is a titanium silicate molecular sieve, belonging to the Pentasil type heteroatom molecular sieve. The TS-1 molecular sieve loaded with Pt is denoted as Pt@TS-1 molecular sieve.

[0038] In the process of synthesizing the EMT / FAU eutectic molecular sieve of the present invention, by adjusting the proportion of NaOH, the proportion of the two-phase molecular sieve can be adjusted. Among them, when the amount of NaOH used is appropriately reduced, it is helpful to form an EMT / FAU eutectic molecular sieve mainly composed of the EMT structure; when the amount of NaOH used is appropriately increased, it is helpful to form an EMT / FAU eutectic molecular sieve mainly composed of the FAU structure.

[0039] The EMT / FAU eutectic molecular sieve synthesized by the present invention using 18-crown-6 as a structure-directing agent has higher crystallinity and purity and better thermal stability. By introducing phosphide in the present invention, the crystallization time can be reduced.

[0040] By subjecting the EMT / FAU eutectic molecular sieve to ammonium ion exchange in the present invention, the Brønsted acid sites are increased to enable polyethylene to initially react to generate olefin intermediates; the olefin intermediates are further hydrogenated at the metal sites provided by the Pt@TS-1 molecular sieve to generate liquid alkanes. This reaction mode of acid site-metal tandem greatly reduces the reaction time and improves the activity of the EMT / FAU eutectic molecular sieve catalyst, and can convert polyethylene into the target product under mild conditions.

[0041] The acid zeolite controllably synthesized by the present invention contains a large number of acid sites. When it is used in tandem with Pt@TS-1 zeolite to catalyze polyethylene, higher reaction rates and liquid fuel yields can be obtained; moreover, the distribution of liquid products is more concentrated. The EMT / FAU eutectic zeolite catalyst prepared by the present invention has better stability, can achieve efficient selective degradation of polyolefin plastics under relatively mild reaction conditions, has universality, and explores a new way to protect the environment and promote resource recovery.

[0042] The technical solutions of the present invention are further described below through specific examples.

[0043] In the following examples, unless otherwise specified, the methods are all conventional methods; unless otherwise specified, the reagents and materials can all be purchased on the market.

[0044] The room temperature is 25 °C. The temperature of the ice-water bath is between 0 °C and 5 °C.

[0045] The mass of silicon particles in the silica sol accounts for 25% of the total mass of the silica sol.

[0046] Example 1 A preparation method of an EMT / FAU eutectic zeolite catalyst includes the following steps: Step 1, preparation of EMT / FAU eutectic zeolite: 0.4 g of sodium hydroxide, 3.7 g of water, 1 g of sodium aluminate, 0.03 g of sodium phosphate, 0.55 g of 18-crown-6 and 10 g of silica sol are stirred at room temperature for 2 h to obtain a mixed solution.

[0047] The mixed solution is aged at 23 °C for 24 h; the aged sol is transferred into a 25 mL crystallization kettle and crystallized at 100 °C for 6 days; after crystallization is completed, it is cooled to room temperature, filtered, washed, dried at 60 °C for 24 h, and then placed in a muffle furnace and heated to 550 °C at a heating rate of 5 °C / min and calcined for 8 h to remove the structure-directing agent 18-crown-6, obtaining EMT / FAU eutectic zeolite.

[0048] Step 2, preparation of acid zeolite: EMT / FAU eutectic zeolite, ammonium chloride and water are weighed according to the mass ratio of 1:3:30; ammonium chloride is dissolved in water, and then EMT / FAU eutectic zeolite is added, and it is treated in a 90 °C water bath for 1.5 h for ammonia exchange of EMT / FAU eutectic zeolite, filtered by suction, dried at 60 °C for 24 h, and then placed in a muffle furnace and heated to 550 °C at a heating rate of 3 °C / min and calcined for 6 h to obtain an acid zeolite with a pH of 6-7.

[0049] Step 3, Preparation of Pt-loaded TS-1 molecular sieve: 40 g of tetraethyl 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 h; then, in a 70 °C water bath, it was first opened and steamed for 30 min, then 30 g of water was added, and stirring and mixing continued for 2.5 h; 48 g of isopropanol was added, and stirring continued for 1 h to obtain the first solution.

[0050] 0.10 g of sodium hydroxide, 2.0 g of water, and 0.12 g of 3-mercaptopropyltrimethoxysilane were stirred and mixed for 20 min, then 6.16 mL of 100 mM H2PtCl6 was added dropwise, and stirring continued for 20 min to obtain the second solution.

[0051] The second solution was slowly added dropwise to the first solution, and stirring continued in a 70 °C water bath for 30 min, then it was transferred to a crystallization kettle and crystallized at 170 °C for 24 h. After crystallization was completed, it was cooled to room temperature, filtered, washed, dried at 60 °C for 24 h, then placed in a muffle furnace and calcined at 550 °C for 4 h to obtain the Pt-loaded TS-1 molecular sieve, denoted as Pt@TS-1 molecular sieve.

[0052] Step 4, Preparation of EMT / FAU eutectic molecular sieve catalyst: The acidic molecular sieve and Pt@TS-1 molecular sieve were stirred and mixed at a mass ratio of 1:1 to obtain the EMT / FAU eutectic molecular sieve catalyst.

[0053] Example 2 A method for preparing an EMT / FAU eutectic molecular sieve catalyst, comprising the following steps: Step 1, Preparation of EMT / FAU eutectic molecular sieve: 0.42 g of sodium hydroxide, 3.7 g of water, 1 g of sodium aluminate, 0.03 g of sodium phosphate, 0.55 g of 18-crown-6, and 10 g of silica sol were stirred at room temperature for 2 h to obtain a mixed solution.

[0054] The mixed solution was aged at 23 °C for 24 h; the aged sol was transferred to a 25 mL crystallization kettle and crystallized at 100 °C for 6 days; after crystallization was completed, it was cooled to room temperature, filtered, washed, dried at 60 °C for 24 h, then placed in a muffle furnace and heated to 550 °C at a heating rate of 5 °C / min and calcined for 8 h to remove the structure-directing agent 18-crown-6 to obtain the EMT / FAU eutectic molecular sieve.

[0055] Step 2, Preparation of acidic molecular sieve: Weigh EMT / FAU eutectic zeolite, ammonium chloride and water according to the mass ratio of 1:3:30; dissolve ammonium chloride in water, then add EMT / FAU eutectic zeolite, and perform ammonia exchange on EMT / FAU eutectic zeolite by water bath treatment at 90 °C for 1.5 h, filter by suction, dry at 60 °C for 24 h, then place it in a muffle furnace, heat up to 550 °C at a heating rate of 3 °C / min, and keep it calcined for 6 h to obtain an acidic zeolite with a pH of 6-7.

[0056] Step 3, Preparation of Pt-loaded TS-1 zeolite: Mix 40 g of tetraethyl orthosilicate, 2.64 g of tetrabutyl titanate and 56.72 g of 25 wt% tetrapropylammonium hydroxide under ice-water bath and stir for 1 h; then under 70 °C water bath, first open the mouth and evaporate for 30 min, then add 30 g of water, and continue to stir and mix for 2.5 h; add 48 g of isopropanol and continue to stir for 1 h to obtain the first solution.

[0057] Stir and mix 0.10 g of sodium hydroxide, 2.0 g of water and 0.12 g of 3-mercaptopropyltrimethoxysilane for 20 min, then dropwise add 6.16 mL of 100 mM H2PtCl6 solution, and continue to stir for 20 min to obtain the second solution.

[0058] Slowly drop the second solution into the first solution, continue to stir in a 70 °C water bath for 30 min, then transfer it to a crystallization kettle, perform crystallization treatment at 170 °C for 24 h. After crystallization is completed, cool to room temperature, filter, wash, dry at 60 °C for 24 h, then place it in a muffle furnace, and calcine at 550 °C for 4 h to obtain Pt-loaded TS-1 zeolite, denoted as Pt@TS-1 zeolite.

[0059] Step 4, Preparation of EMT / FAU eutectic zeolite catalyst: Stir and mix the acidic zeolite and Pt@TS-1 zeolite according to the mass ratio of 1:1 to obtain an EMT / FAU eutectic zeolite catalyst.

[0060] Test 1: Scanning electron microscopy and X-ray diffraction analysis.

[0061] Perform scanning electron microscopy analysis on the EMT / FAU eutectic zeolite prepared in Example 1 and Example 2, and the results are as Figure 1 and Figure 2 shown.

[0062] From Figure 1 and Figure 2It can be seen that a small amount of FAU zeolite particles grow on the EMT zeolite. By slightly increasing the NaOH content, the proportion of FAU zeolite in the EMT / FAU eutectic zeolite increases, and the crystals show a high degree of twinning.

[0063] X-ray diffraction analysis was performed on the EMT / FAU eutectic zeolites prepared in Example 1 and Example 2, and the results are as Figure 3 shown.

[0064] It can be seen from Figure 3 that there are three peaks in the range of 5° ≤ 2θ ≤ 7°, which are the 100, 002, and 101 reflections of the hexagonal EMT zeolite, respectively. The position of the 002 reflection of the EMT zeolite coincides with the position of the 111 reflection of the cubic FAU zeolite, and with the increase of NaOH, the FAU crystal form tends to be generated.

[0065] Based on the above analysis, it can be known that by slightly increasing the NaOH content, it is directly manifested as an increase in the particle size of the surface FAU zeolite, and by comparing the characteristic peaks of X-ray diffraction, it can be seen that the 002 reflection peak of Example 2 is more prominent.

[0066] Transmission electron microscopy analysis was performed on the Pt@TS-1 zeolite of Example 1, and the results are as Figure 4 shown.

[0067] It can be seen from Figure 4 that the Pt@TS-1 zeolite presents a cubic shape, has a high crystallinity, conforms to the characteristic structure of the zeolite, and Pt does not show obvious agglomeration, that is, there is no obvious metal cluster > 10 nm, and it is uniformly encapsulated inside the TS-1 zeolite.

[0068] Next, the polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic zeolite catalyst prepared in the above Example 1 and Example 2.

[0069] Application Example 1 The polyethylene hydrocracking reaction was carried out using the EMT / FAU eutectic zeolite catalyst prepared in Example 1. The specific method includes the following steps: 1 g of low-density polyethylene with a melt index of 20 g to 30 g / 10 min and a particle size of ~1000 mesh and 0.2 g of EMT / FAU eutectic zeolite catalyst were added to a high-pressure reactor, stirred and mixed evenly, and reacted at 260 °C and 2 Mpa H2 for 1 h. After the high-pressure reactor was cooled to room temperature, the remaining H2 and a small amount of gaseous alkanes in the high-pressure reactor were collected. The remaining solid and liquid products were separated by extraction with dichloromethane, and the extract and solid products were separated by filtration; the collected extract contained the liquid products of the reaction. The liquid products and the collected gas were analyzed by gas chromatography. Among them, the liquid product was liquid alkanes, the yield of the liquid product was 91.3%, and the selectivity of C5-C9 hydrocarbons reached 86.5%. The gas yield was 5.4%.

[0070] Application Example 2 The EMT / FAU eutectic zeolite catalyst prepared in Example 2 was used for the hydrogenation cracking reaction of polyethylene. The specific method included the following steps: 1 g of low-density polyethylene with a melt index of 20 g to 30 g / 10 min and a particle size of ~1000 mesh and 0.2 g of EMT / FAU eutectic zeolite catalyst were added to a high-pressure reactor, stirred and mixed evenly, and reacted at 260 °C and 2 Mpa H2 for 1 h. After the high-pressure reactor was cooled to room temperature, the remaining H2 and a small amount of gaseous alkanes in the high-pressure reactor were collected. The remaining solid and liquid products were separated by extraction with dichloromethane, and the extract and solid products were separated by filtration; the collected extract contained the liquid products of the reaction. The liquid products and the collected gas were analyzed by gas chromatography. Among them, the liquid product was liquid alkanes, the yield of the liquid product was 93.1%, and the selectivity of C5-C9 hydrocarbons reached 88.5%. The gas yield was 6.2%.

[0071] Application Example 3 The EMT / FAU eutectic zeolite catalyst prepared in Example 1 was used for the hydrogenation cracking reaction of polyethylene. The first hydrogenation cracking reaction of polyethylene was carried out according to the method of Application Example 1. The liquid products and the EMT / FAU eutectic zeolite catalyst of the first hydrogenation cracking reaction of polyethylene were collected and separated. 0.2 g of the separated EMT / FAU eutectic zeolite catalyst and 1 g of low-density polyethylene with a melt index of 20 g to 30 g / 10 min and a particle size of ~1000 mesh were used to repeat the hydrogenation cracking reaction of polyethylene according to the method of Application Example 1. The number of repeated reactions was 5 times. The liquid products and the collected gas after 5 cycles of reactions were analyzed by gas chromatography.

[0072] Application Example 4 The EMT / FAU eutectic zeolite catalyst prepared in Example 1 was used for the hydrocracking reaction of polyethylene. The hydrocracking reaction of polyethylene was carried out according to the method of Application Example 1, except that the low-density polyethylene with a melt index of 20 g to 30 g / 10 min and a particle size of ~1000 mesh was replaced with high-density polyethylene spheres.

[0073] Application Example 5 The EMT / FAU eutectic zeolite catalyst prepared in Example 1 was used for the hydrocracking reaction of polyethylene. The hydrocracking reaction of polyethylene was carried out according to the method of Application Example 1, except that the low-density polyethylene with a melt index of 20 g to 30 g / 10 min and a particle size of ~1000 mesh was replaced with high-density polypropylene.

[0074] Test 2: Analysis of hydrocracked polyethylene products.

[0075] The hydrocracking reaction of polyethylene was carried out using the EMT / FAU eutectic zeolite catalysts prepared in Example 1 and Example 2, and the hydrocracked polyethylene products collected were analyzed by gas chromatography. The results are as Figure 5 and Figure 6 shown. At the same time, the liquid products and the collected gases after 5 cycles of reaction in Application Example 3 were analyzed by gas chromatography; the hydrocracked polyethylene products collected in Application Example 4 and Application Example 5 were analyzed by gas chromatography; the results are shown in Table 1.

[0076] Table 1 Yields of liquid products and gases

[0077] From Table 1 combined with Figure 5 and Figure 6 it can be seen that in Application Examples 1 to 5, the liquid products are concentrated in C5 - C9 hydrocarbons, with a relatively high liquid fuel yield. The tandem application of the eutectic zeolite and Pt@TS-1 improves the hydrocracking rate and realizes the conversion of the catalytic product distribution of polyolefins to narrow-distribution oil alkanes.

[0078] 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%. This indicates that the EMT / FAU eutectic zeolite catalyst prepared in the examples of the present invention has relatively good stability.

[0079] The results of Application Example 1, Application Example 4 and Application Example 5 show that the EMT / FAU eutectic zeolite catalyst prepared in the examples of the present invention has high activity and high liquid product yields for polyolefin raw materials such as low-density polyethylene, high-density polyethylene spheres and high-density polypropylene, showing good universality.

[0080] In summary, as analyzed above, the acid zeolite prepared by controllable synthesis in the embodiments of the present invention contains a large number of acid sites. When it is used in tandem with Pt@TS-1 zeolite to catalyze polyethylene, higher reaction rates and liquid fuel yields can be obtained; moreover, the distribution of liquid products is more concentrated. The EMT / FAU eutectic zeolite catalyst prepared in the embodiments of the present invention has relatively good stability, can achieve efficient selective degradation of polyolefin plastics under relatively mild reaction conditions, has universality, and explores a new way for environmental protection and resource recovery promotion.

[0081] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An EMT / FAU eutectic zeolite catalyst, characterized in that, The EMT / FAU eutectic zeolite catalyst is obtained by physically mixing an acidic zeolite and a Pt-loaded TS-1 zeolite, wherein the mass ratio of the acidic zeolite to the Pt-loaded TS-1 zeolite is 1:1; The acidic zeolite is obtained by ion-exchanging the EMT / FAU eutectic zeolite in an inorganic ammonium salt solution to introduce ammonium ions to increase Brønsted acid sites, followed by drying and calcination to obtain the acidic zeolite.

2. The EMT / FAU eutectic zeolite catalyst according to claim 1, wherein The acidic zeolite is prepared by the following method: The EMT / FAU eutectic zeolite and the inorganic ammonium salt solution are ion-exchanged at 75°C to 95°C to introduce ammonium ions, filtered and dried, and then calcined at 350°C to 550°C to convert the ammonium ions into acidic sites, obtaining the acidic zeolite.

3. The EMT / FAU eutectic zeolite catalyst according to claim 2, wherein The pH of the acidic zeolite is 6 to 7; The mass ratio of the EMT / FAU eutectic zeolite to the inorganic ammonium salt solution is 5 to 11:33; The inorganic ammonium salt solution is obtained by mixing an inorganic ammonium salt and water in a mass ratio of 1 to 4:11; The inorganic ammonium salt is ammonium chloride or ammonium sulfate.

4. The EMT / FAU eutectic zeolite catalyst according to claim 1, wherein The Pt-loaded TS-1 zeolite is prepared by the following method: The silicon source, titanium source, and tetrapropylammonium hydroxide are stirred and mixed in an ice-water bath, and then stirred and reacted in an aqueous alcohol solution at 50°C to 90°C to obtain a first solution; Using H2PtCl6 as the platinum precursor, the H2PtCl6 solution and 3-mercaptopropyltrimethoxysilane solution are stirred and mixed to obtain a second solution containing the Pt precursor; The first solution and the second solution containing the Pt precursor are mixed and reacted at 50°C to 90°C, then subjected to crystallization treatment 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 zeolite.

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

6. The EMT / FAU eutectic zeolite catalyst according to claim 4, wherein 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 to 0.2:1 to 10; The dosage ratio of H2PtCl6 to 3-mercaptopropyltrimethoxysilane is 0.616 mmol:0.05 to 0.2 g.

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

8. The EMT / FAU eutectic molecular sieve catalyst according to claim 7, wherein 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, the Al source, sodium phosphate, 18-crown-6, and silica sol is 0.4 to 0.42:1:0.03:0.55:

10.

9. A preparation method of an EMT / FAU eutectic molecular sieve catalyst, characterized in that, Including the following steps: The EMT / FAU eutectic zeolite is subjected to ion exchange in an inorganic ammonium salt solution to introduce ammonium ions to increase the Brønsted acid sites, and after drying, it is calcined to obtain an acidic zeolite; The acidic zeolite and the TS-1 zeolite loaded with Pt are physically mixed to obtain an EMT / FAU eutectic zeolite catalyst; The EMT / FAU eutectic zeolite catalyst is the EMT / FAU eutectic zeolite catalyst described in any one of claims 1 to 8.

10. Application of an EMT / FAU eutectic zeolite catalyst in polyolefin hydrocracking, characterized in that, The specific application method is as follows: In a hydrogen atmosphere with a hydrogen pressure of 0.5 Mpa to 4 Mpa, the waste polyolefin and the EMT / FAU eutectic zeolite catalyst are stirred and reacted at 220 °C to 260 °C, and after the reaction is completed, the hydrocracking products are collected; The EMT / FAU eutectic zeolite catalyst is the EMT / FAU eutectic zeolite catalyst described in any one of claims 1 to 8; The mass ratio of the waste polyolefin to the EMT / FAU eutectic zeolite catalyst is 1 to 3:0.2.

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