Pt / ZSM-5 supported catalyst for high-density polyethylene catalytic cracking reaction and its preparation method and application

Abstract

The present invention discloses a Pt / ZSM-5 supported catalyst for high-density polyethylene catalytic cracking reaction and its preparation method and application, which belongs to the technical field of supported metal catalysts. The method first uniformly loads Pt nanoparticles onto ZSM-5 seed crystals by an impregnation method, and then prepares the final Pt-loaded Pt / ZSM-5 catalyst in ZSM-5 by a solvent-free and organic template-free solid-phase method. The Pt / ZSM-5 supported catalyst prepared by the present invention is applied to the catalytic cracking reaction of high-density polyethylene, and the interaction between the precious metal and the molecular sieve carrier is used to effectively regulate the distribution of polyethylene catalytic cracking reaction products, thereby obtaining a higher liquid hydrocarbon yield, and is an efficient supported catalyst. The present invention provides an environmentally friendly, safe and low-cost strategy for the cracking of waste plastics and the preparation of supported molecular sieve catalysts.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-metal supported catalysts, and in particular to a Pt / ZSM-5 supported catalyst for high-density polyethylene catalytic cracking reaction, and a preparation method and application thereof. Background Art

[0002] Modern human life is highly dependent on plastic polymers. In 2019, global plastic production reached 368 million tons, and the plastics market continues to grow, potentially reaching 1.2 billion tons by 2050. However, over 75% of the plastic produced annually is discarded after a single use, either for landfill or mechanical recycling. Consequently, the accumulation of waste plastics has caused serious environmental pollution, with microplastics even entering ecosystems through biological cycles. Although many countries have enacted plastic restrictions and prioritized the development of biodegradable plastics, how to deal with current plastic waste remains a challenge. Incineration is a commonly used strategy for down-cycling, but it produces greenhouse gases such as CO2 and toxic byproducts. In contrast, catalytic cracking of waste plastics is a commonly used approach to selectively obtain high-value-added products, particularly petroleum-derived chemicals, thereby achieving an up-cycling process.

[0003] Zeolite catalysts (such as H-ZSM-5, HY, and H-Beta) are often used for the catalytic cracking of high-density polyethylene, but require a relatively high temperature (usually above 400°C) to crack the CC bonds of the polymer. High temperatures require a lot of energy consumption and also produce low-value-added low-carbon alkane gases. The use of zeolite-loaded noble metal-based catalysts can reduce the reaction temperature and obtain high-yield saturated liquid fuel products. In the process of zeolite-catalyzed polymer cracking, acid sites play an important role in the reaction mechanism. There is a strong interaction between the noble metal and the Al species in the pores of the zeolite, resulting in a decrease in the surface electron density of the metal particles. The presence of Pt near the acid sites of the zeolite in the Pt / HY catalyst causes the reaction intermediates to be confined to the zeolite micropores. Hydrocarbons with larger carbon numbers show obvious diffusion limitations, resulting in excessive cracking and the appearance of light products. Therefore, the degree of coupling between the molecular sieve acid sites and the precious metal particles is a key factor in determining the activity of the catalyst. Therefore, by regulating the degree of coupling between the metal active sites and the molecular sieve zeolite acid sites, the performance of the high-density polyethylene cracking catalyst can be effectively regulated, thereby achieving the goal of converting high-density polyethylene into liquid fuel with high added value under mild conditions.

[0004] The hydrothermal synthesis process of molecular sieves has the following characteristics: high production cost, large amount of wastewater, and NO generated during calcination. xDisadvantages include the presence of pollutants such as CO2 and limited mass transfer due to large crystal size. Under relatively high temperatures and high pressures, molecular sieves with different morphologies and pore structures can be obtained using organic templates as structure-directing agents. Organic templates are relatively expensive, accounting for over 90% of the total production cost of zeolite molecular sieves. Precious metals are loaded onto the surface of the molecular sieve carrier, which is prone to agglomeration and shedding during the catalytic process, reducing the number of active sites. Therefore, it is necessary to develop new, environmentally friendly, safe, and efficient methods for preparing molecular sieves, while also encapsulating precious metals to obtain highly efficient catalysts. Summary of the Invention

[0005] The present invention aims to provide a Pt / ZSM-5 supported catalyst for the catalytic cracking of high-density polyethylene (HDPE), as well as its preparation method and application. Pt nanoparticles are uniformly loaded onto ZSM-5 seed crystals using an impregnation method, followed by a solvent-free, organic-template-free method to prepare the final Pt / ZSM-5 catalyst. This method utilizes the interaction between the metal and the molecular sieve support to regulate the catalyst's acid sites and electron density, enabling the catalyst to modulate its performance in the catalytic cracking of HDPE. This allows the prepared catalyst to produce a high yield of liquid hydrocarbons under relatively mild conditions, providing an environmentally friendly, safe, and efficient strategy for the cracking of waste plastics and the preparation of supported metal catalysts.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A Pt / ZSM-5 supported catalyst for high-density polyethylene catalytic cracking reaction is formed by uniformly loading noble metal Pt nanoparticles on a ZSM-5 carrier, wherein the ZSM-5 carrier has an MFI structure.

[0008] In the Pt / ZSM-5 supported catalyst, the loading amount of Pt nanoparticles is 2.0-5.0 wt.%.

[0009] The method for preparing the Pt / ZSM-5 supported catalyst for high-density polyethylene catalytic cracking reaction: the method firstly uniformly loads Pt nanoparticles onto ZSM-5 seed crystals by an impregnation method, and then prepares the final Pt / ZSM-5 catalyst by a solvent-free and organic template-free solid-phase method.

[0010] The method specifically comprises the following steps:

[0011] (1) Synthesis of ZSM-5 molecular sieve seed crystals: Tetraethyl orthosilicate (TEOS) is added to deionized water containing a certain amount of tetrapropylammonium hydroxide (TPAOH) to obtain a milky white solution I. An appropriate amount of sodium metaaluminate is added to deionized water to obtain a clear solution II. After solution I is fully stirred at room temperature for 10-12 hours, solution II is added to solution I and fully stirred for 5-7 hours to obtain solution III. Solution III is poured into a reactor and reacted in an oven at 160-180°C for 20-24 hours. The resulting precipitate is then centrifuged and washed with deionized water and anhydrous ethanol, and then transferred to an oven at 60-80°C for drying. The precipitate is ground into powder and treated in an air atmosphere at 400-600°C for 5-7 hours to obtain ZSM-5 molecular sieve seed crystals.

[0012] (2) dissolving an appropriate amount of chloroplatinic acid hydrate in anhydrous ethanol, stirring thoroughly until completely dissolved, adding an appropriate amount of ZSM-5 molecular sieve seed crystals prepared in step (1), ultrasonicating until the seed crystals are completely and evenly dispersed, and then placing the resulting dispersion in an oven at 60° C. for 20-24 hours to obtain a catalyst precursor loaded with a metal salt;

[0013] (3) transferring the catalyst precursor obtained in step (2) to an oven at 80°C for drying;

[0014] (4) heat-treating the catalyst precursor treated in step (3) in a mixed atmosphere of hydrogen and argon to obtain Pt / ZSM-5 seed crystals;

[0015] (5) The Pt / ZSM-5 seed crystals obtained in step (4) are placed in an agate mortar with an appropriate amount of sodium metasilicate nonahydrate, aluminum sulfate 18hydrate and fumed silica, and ground for 10-20 minutes to uniformly mix. The obtained solid white powder is placed in a reactor and reacted in an oven at 160-200°C for 10-14 hours. The obtained product is washed alternately with deionized water and ethanol twice or more, filtered, dried in an oven at 80°C, and heat-treated in a mixed atmosphere of hydrogen and argon at 300-550°C for 5-7 hours to obtain the Pt / ZSM-5 supported catalyst.

[0016] In the above step (1), the volume ratio of tetraethyl orthosilicate and tetrapropylammonium hydroxide in the milky white solution I is 1 (0.8-1.5); the mass ratio of sodium metaaluminate and tetraethyl orthosilicate in the solution III is 1.0:(55-65).

[0017] In the above step (2), the ratio of the chloroplatinic acid hydrate to the ZSM-5 molecular sieve seed crystals is determined by the required loading amount.

[0018] In the above steps (4) and (5), the heating rate during the heat treatment process is 2-5°C / min, the treatment temperature is 300-550°C, and the holding time is 2-4 hours.

[0019] In the above steps (4) and (5), the hydrogen content in the mixed atmosphere of hydrogen and argon is 15 to 25 vol.%.

[0020] In the above step (5), the weight ratio of the Pt / ZSM-5 seed crystals, sodium metasilicate nonahydrate, aluminum sulfate 18hydrate and fumed silica is 1:(6-10):(2-5):(5-10).

[0021] The Pt / ZSM-5 supported catalyst is applied to the catalytic cracking reaction of high-density polyethylene, with a reaction temperature of 250-300° C., a conversion rate greater than 70%, and a liquid hydrocarbon yield of 40% to 60%.

[0022] The present invention has the following advantages and beneficial effects:

[0023] 1. The method of the present invention utilizes the interaction between metal and molecular sieve support to regulate the acid sites and electron density of the catalyst, thereby achieving the regulation of the catalytic cracking reaction performance of high-density polyethylene, so that the prepared catalyst can produce a higher liquid hydrocarbon yield under relatively mild conditions, providing a simple and efficient strategy for the cracking of waste plastics and the preparation of supported metal catalysts.

[0024] 2. The present invention prepares the Pt / ZSM-5 catalyst by a solvent-free and organic template-free solid-phase method. The ZSM-5 carrier presents a classic MFI structure, and the loaded metal Pt is uniformly dispersed on the carrier without agglomeration.

[0025] 3. The performance test after catalytic cracking of high-density polyethylene in the present invention confirms that the Pt / ZSM-5 supported catalyst is applied to the catalytic cracking reaction of high-density polyethylene, with a conversion rate greater than 70% and a liquid hydrocarbon yield of about 50%, indicating that the catalyst has efficient plastic cracking performance and is an excellent supported catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 X-ray diffraction (XRD) spectra, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) images of Pt / ZSM-5, ZSM-5 and Pt-ZSM-5 catalysts; wherein: (a) is the XRD spectra of ZSM-5, Pt / ZSM-5 and Pt-ZSM-5 catalysts, (b) is the XPS spectra of Pt / ZSM-5 and Pt-ZSM-5 catalysts, (c) is the SEM image of ZSM-5 catalyst, (d) is the SEM image of Pt / ZSM-5 catalyst, and (e) is the SEM image of Pt-ZSM-5 catalyst;

[0027] Figure 2 Transmission electron microscopy (TEM) images, high-resolution transmission electron microscopy (HRTEM) images, scanning transmission electron microscopy (STEM) images, and energy dispersive spectrum (EDX-mapping) images of Pt / ZSM-5, ZSM-5, and Pt-ZSM-5 catalysts; (a) and (b) are high-resolution TEM images of ZSM-5 sections, (c) is a TEM image of the Pt-ZSM-5 catalyst, (d) is a TEM image and HRTEM image of the Pt / ZSM-5 catalyst section, and (e) is a STEM image and EDX-mapping image of Pt / ZSM-5.

[0028] Figure 3 To evaluate the performance of Pt / ZSM-5, ZSM-5 and Pt-ZSM-5 catalysts in catalytic cracking reaction of high density polyethylene. DETAILED DESCRIPTION

[0029] The present invention provides a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene, a preparation method thereof, and an application thereof. The present invention is further described below with reference to embodiments and accompanying drawings.

[0030] Example 1:

[0031] The process of preparing the Pt / ZSM-5 catalyst in this embodiment is as follows:

[0032] 1. Add 4.285 g of tetraethyl orthosilicate (TEOS) to 6.23 mL of deionized water containing 4.89 g of tetrapropylammonium hydroxide (TPAOH) to obtain a milky white solution I. Add 0.073 g of sodium metaaluminate to 6 mL of deionized water to obtain a clear solution II. After solution I is fully stirred at room temperature for 12 hours, solution II is added to solution I and fully stirred for 5 hours to obtain solution III. Pour solution III into a reactor and react in a 170°C oven for 24 hours. Then, the resulting precipitate is centrifuged and washed with deionized water and anhydrous ethanol, and transferred to an 80°C oven for drying; grind it into a powder and treat it in an air atmosphere at 550°C for 6 hours to obtain ZSM-5 molecular sieve seed crystals.

[0033] 2. Dissolve 4 mg of chloroplatinic acid hydrate in 50 mL of ethanol solution and stir thoroughly until completely dissolved. Add 200 mg of ZSM-5 molecular sieve seed crystals prepared in step (1) and sonicate for 2 hours until the seed crystals are completely and evenly dispersed. Then, immerse the resulting dispersion in a 60°C oven for 24 hours to obtain a catalyst precursor loaded with metal salts; then transfer to an 80°C oven for drying.

[0034] 3. The sample obtained in step 2 was heat treated in a mixture of hydrogen and argon (H2 volume ratio of 20%), and the temperature was increased to 350°C at a heating rate of 5°C / min and kept at this temperature for 2 hours, then increased to 550°C and kept at this temperature for 2 hours, and then cooled to room temperature to obtain Pt / ZSM-5 seed material.

[0035] 4. The 0.17g Pt / ZSM-5 seed crystal obtained in step 3 is placed in an agate mortar with 1.5g sodium metasilicate nonahydrate, 0.65g aluminum sulfate 18hydrate, and 1.35g fumed silica, and ground for 20 minutes to uniformly mix. The gained solid white powder is placed in a reactor and reacted in a 170°C baking oven for 13 hours. The products therefrom are washed three times with deionized water and ethanol alternately, filtered off with suction, and heat-treated in a hydrogen and argon mixed gas (H2 volume ratio is 20%) at 80°C. The thermal treatment process is: heated to 350°C and maintained at this temperature for 2 hours at a heating rate of 5°C / min, then to 550°C and maintained at this temperature for 2 hours, and then cooled to room temperature to obtain the Pt / ZSM-5 supported catalyst.

[0036] In the Pt / ZSM-5 catalyst prepared in this example, the loading amount of the noble metal Pt nanoparticles was about 1.0 wt.%.

[0037] Comparative Example 1:

[0038] The process of preparing the catalyst in this example is different from that in Example 1 in that steps 2 and 3 are omitted.

[0039] Comparative Example 2:

[0040] The process of preparing the catalyst in this example is as follows:

[0041] 1. Add 4.285 g of tetraethyl orthosilicate (TEOS) to 6.23 mL of deionized water containing 4.89 g of tetrapropylammonium hydroxide (TPAOH) to obtain a milky white solution I. Add 0.073 g of sodium metaaluminate to 6 mL of deionized water to obtain a clear solution II. After solution I is fully stirred at room temperature for 12 hours, solution II is added to solution I and fully stirred for 5 hours to obtain solution III. Pour solution III into a reactor and react in a 170°C oven for 24 hours. Then, the resulting precipitate is centrifuged and washed with deionized water and anhydrous ethanol, and transferred to an 80°C oven for drying; grind it into a powder and treat it in an air atmosphere at 550°C for 6 hours to obtain ZSM-5 molecular sieve seed crystals.

[0042] 2. Place 0.17 g of ZSM-5 seed crystals obtained in step 1, 1.5 g of sodium metasilicate nonahydrate, 0.65 g of aluminum sulfate 18-hydrate, and 1.35 g of fumed silica in an agate mortar and grind for 20 minutes to uniformly mix. Place the solid white powder in a reactor and react in an oven at 170°C for 13 hours to obtain a ZSM-5 catalyst.

[0043] 3. Dissolve 4 mg of chloroplatinic acid hydrate in 50 mL of ethanol solution and stir thoroughly until completely dissolved. Add 200 mg of the ZSM-5 molecular sieve prepared in step (2) and sonicate for 2 hours until the seed crystals are completely and evenly dispersed. Then, immerse the resulting dispersion in a 60°C oven for 24 hours to obtain a catalyst precursor loaded with metal salts; then transfer to an 80°C oven for drying.

[0044] 4. The sample treated in step 3 was heat treated in a mixture of hydrogen and argon (H2 volume ratio is 20%), and the temperature was increased to 350°C at a heating rate of 5°C / min and kept at a constant temperature for 2 hours, then increased to 550°C and kept at a constant temperature for 2 hours, and then cooled to room temperature to obtain Pt-ZSM-5 material.

[0045] The XRD patterns, SEM patterns and XPS patterns of the Pt / ZSM-5 catalyst, ZSM-5 catalyst and Pt-ZSM-5 catalyst prepared in Example 1, Comparative Example 1 and Comparative Example 2 are shown in FIG. Figure 1 As shown; TEM image and EDX-mapping image are as follows Figure 2 shown.

[0046] The Pt / ZSM-5 catalyst prepared in Example 1 is as follows Figure 1 (d) Figure 2 (d) and Figure 2 As shown in (e), the SEM image shows the Pt / ZSM-5 as a cubic block with uniform size. A cross-section TEM image reveals that the Pt nanoparticles are loaded both internally and on the surface of the support. The Pt nanoparticles are small and uniformly dispersed. STEM and EDX-mapping images demonstrate the uniform distribution of Al, Si, O, and Pt elements.

[0047] The ZSM-5 catalyst prepared in Comparative Example 1 is as follows Figure 1 (c) and Figure 2 As shown in (d), ZSM-5 has a cubic block morphology, no nanoparticles on the surface, and uniform size.

[0048] The Pt-ZSM-5 catalyst prepared in Comparative Example 2 is as follows Figure 1 (b), (e) and Figure 2As shown in (c), the SEM image shows that the Pt-ZSM-5 is a block with uneven size. The TEM image of the section shows that the support surface is loaded with precious metal Pt nanoparticles. The Pt nanoparticles are large in size and exhibit agglomeration. The XPS image shows that the zero-valent Pt content is lower than that in Example 1, indicating the encapsulation effect of the molecular sieve on the Pt nanoparticles.

[0049] Example 2:

[0050] The catalyst prepared in Example 1 was applied to the catalytic cracking reaction of high-density polyethylene, and the process was as follows:

[0051] The catalytic cracking reaction of high-density polyethylene was carried out in a 50ml stainless steel autoclave with a quartz liner. First, 100mg of high-density polyethylene and 100mg of the Pt / ZSM-5 catalyst prepared in Example 1 were added to the quartz liner and mixed evenly. The quartz liner was placed in the reactor and sealed, argon was introduced to replace the gas in the reactor and the airtightness was checked, followed by hydrogen to replace the gas in the reactor, and finally 2MPa of hydrogen was introduced, and heated and stirred at 270°C for 12 hours. After the reaction was completed, the reactor was naturally cooled to room temperature, and the gas products were collected for chromatographic analysis; then the liner was taken out, 10mL of chloroform was added as a solvent, 30μL of mesitylene as an internal standard, and the mixture was evenly mixed. A certain amount of solution was extracted and filtered through an organic filter head into a chromatographic bottle for chromatographic analysis; the remaining solid was filtered, dried and weighed.

[0052] When the catalyst is used in the catalytic cracking reaction of high-density polyethylene, the conversion rate is greater than 70% and the liquid hydrocarbon yield is greater than 50%, indicating that the catalyst has excellent high-density polyethylene plastic cracking performance.

[0053] Comparative Example 3:

[0054] The catalyst prepared in Comparative Example 1 was applied to the catalytic cracking reaction of high-density polyethylene, and the process was the same as that of Example 2.

[0055] After the catalyst of Comparative Example 1 was applied, the conversion rate was 20% and the liquid hydrocarbon yield was 18%, indicating that the catalytic conversion rate of the catalyst for high-density polyethylene was relatively low.

[0056] Comparative Example 4:

[0057] The catalyst prepared in Comparative Example 2 was applied to the catalytic cracking reaction of high-density polyethylene, and the process was the same as in Example 2.

[0058] After the catalyst of Comparative Example 2 was applied, the conversion rate was 40% and the liquid hydrocarbon yield was 30%, indicating that the catalyst had a poor effect on regulating the distribution of catalytic products of high-density polyethylene.

[0059] The performance comparison results of high density polyethylene catalytic cracking reaction in Example 2, Comparative Example 3 and Comparative Example 4 are as follows: Figure 3 shown.

[0060] The above description is 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. A method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene, characterized by: The method comprises the following steps: (1) Synthesis of ZSM-5 molecular sieve seed crystals: Tetraethyl orthosilicate is added to deionized water containing a certain amount of tetrapropylammonium hydroxide to obtain a milky white solution I. An appropriate amount of sodium aluminate is added to deionized water to obtain a clear solution II. After solution I is fully stirred at room temperature for 10-12 hours, solution II is added to solution I and fully stirred for 5-7 hours to obtain solution III. Solution III is poured into a reactor and reacted in an oven at 160-180°C for 20-24 hours. The resulting precipitate is then centrifuged and washed with deionized water and anhydrous ethanol, and then transferred to an oven at 60-80°C for drying. The dried product is ground into powder in a mortar and then treated in an air atmosphere at 400-600°C for 5-7 hours to obtain ZSM-5 molecular sieve seed crystals. (2) dissolving an appropriate amount of chloroplatinic acid hydrate in anhydrous ethanol, stirring thoroughly until completely dissolved, adding an appropriate amount of ZSM-5 molecular sieve seed crystals prepared in step (1), ultrasonicating until the seed crystals are completely and evenly dispersed, and then placing the resulting dispersion in a 60°C oven for 20-24 hours to obtain a catalyst precursor loaded with metal salts; (3) Transfer the catalyst precursor obtained in step (2) to an oven at 80°C for drying; (4) heat-treating the catalyst precursor treated in step (3) in a mixed atmosphere of hydrogen and argon to obtain Pt / ZSM-5 seed crystals; (5) The Pt / ZSM-5 seed crystals obtained in step (4) are placed in an agate mortar with an appropriate amount of sodium metasilicate nonahydrate, aluminum sulfate 18hydrate and fumed silica, and ground for 10-20 minutes to uniformly mix them. The obtained solid white powder is placed in a reactor and reacted in an oven at 160-200°C for 10-14 hours. The obtained solid is alternately washed with deionized water and ethanol, filtered and dried in an oven at 80°C, and heat-treated at 300-550°C in a mixed gas of hydrogen and argon for 5-7 hours to obtain the Pt / ZSM-5 supported catalyst.

2. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking of high-density polyethylene according to claim 1, wherein: In step (1), the volume ratio of tetraethyl orthosilicate and tetrapropylammonium hydroxide in the milky white solution I is 1: (0.8-1.5); the mass ratio of sodium metaaluminate and tetraethyl orthosilicate in the solution III is 1.0: (55-65).

3. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene according to claim 1, characterized in that: In step (2), the ratio of the chloroplatinic acid hydrate to the ZSM-5 molecular sieve seed crystals is determined by the required loading amount. In the Pt / ZSM-5 supported catalyst, the loading amount of Pt nanoparticles is 2.0-5.0 wt.%.

4. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene according to claim 1, characterized in that: In step (4), the heating rate during the heat treatment process is 2-5°C / min, the treatment temperature is 300-550°C, and the holding time is 2-4 hours.

5. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene according to claim 1, characterized in that: In step (5), the heating rate during the heat treatment process is 2 to 5 °C / min.

6. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene according to claim 1, characterized in that: In steps (4) and (5), the hydrogen content in the hydrogen and argon mixed atmosphere is 15 to 25 vol.%.

7. The method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking of high-density polyethylene according to claim 1, wherein: In step (5), the weight ratio of the Pt / ZSM-5 seed crystal, sodium metasilicate nonahydrate, aluminum sulfate 18hydrate and fumed silica is 1: (6-10): (2-5): (5-10).

8. Use of a catalyst prepared by the method for preparing a Pt / ZSM-5 supported catalyst for catalytic cracking reaction of high-density polyethylene according to any one of claims 1 to 7, characterized in that: The Pt / ZSM-5 supported catalyst is used in the catalytic cracking reaction of high-density polyethylene, with a reaction temperature of 250-300° C., a conversion rate greater than 70%, and a liquid hydrocarbon yield of 40-60%.

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