Polyolefin plastic catalytic degradation method with low methane selectivity
The pyrolysis reaction using a mixed catalyst of M/Al2O3-WO3 solved the problem of poor product selectivity in the degradation of polyolefin plastics, achieving efficient catalytic degradation with low methane selectivity and improving the selectivity and yield of liquid products.
Patent Information
- Application Number
- CN202511413414.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2025-11-14
AI Technical Summary
Existing methods for degrading polyolefin plastics suffer from poor product selectivity, particularly high methane selectivity, and low catalytic activity, leading to environmental pollution and increased economic costs.
A mixed catalyst of M/Al2O3-WO3, where M is a noble metal or a non-noble metal, was prepared by physical mixing or impregnation. The catalyst was then subjected to a pyrolysis reaction with polyolefin plastic in the presence of hydrogen. The reaction conditions were controlled to reduce the selectivity of methane and improve the selectivity and yield of the liquid products.
It achieves efficient degradation of polyolefin plastics, with methane selectivity of less than 0.1% in gaseous products and selectivity of up to 90% in liquid products, of which C5-C15 product selectivity exceeds 90%. The catalyst is simple to synthesize and can be applied on a large scale.
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Figure CN120944576A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyolefin plastic degradation technology, and more particularly to a method for catalytic degradation of polyolefin plastics with low methane selectivity. Background Technology
[0002] Plastics, as a synthetic polymer primarily derived from fossil fuels, have been widely used across various industries due to their low cost, light weight, durability, processability, and vast chemical diversity. Over the past few decades, global plastic production has grown exponentially, but less than 10% of plastics are recycled; the rest are disposed of through incineration, landfill, or direct disposal. This not only causes severe environmental pollution but also represents a huge waste of carbon resources. Polyolefin plastics, due to their inert structure, are difficult to degrade in nature, causing serious damage to soil, water resources, and ecosystems. Furthermore, with the escalating global energy crisis, finding sustainable ways to utilize resources has become particularly urgent. Recycling and reusing plastic waste can conserve significant amounts of fossil resources such as oil, alleviate pressure on natural resource extraction, and achieve sustainable resource utilization.
[0003] The recycling of polyolefin plastics includes secondary recycling and chemical recycling. Secondary recycling involves recovering used plastics from various sources, which are often contaminated, and the mechanical properties of recycled plastic products often decline. Chemical recycling refers to converting plastics into valuable chemical substances through chemical reforming processes such as pyrolysis. However, polyolefins have inert C-C and C-H bonds with high bond energies, typically requiring high energy consumption. Catalytic pyrolysis, carried out under the action of a catalyst, can lower the temperature and shorten the reaction time. Currently, supported noble metal-based (platinum, ruthenium, palladium, etc.) or non-noble metal-based (nickel, cobalt, copper, etc.) catalysts for the degradation of polyolefin plastics exhibit high activity in degrading polyolefins, but they often produce large amounts of the low-value greenhouse gas methane—whose greenhouse effect is 22 times that of carbon dioxide, exacerbating environmental problems. Furthermore, the liquid products of polyolefin plastic degradation by supported metal catalysts have complex compositions and a wide carbon number distribution (C5-C6). 40 This increases the economic cost of subsequent separation and application. Rorrer et al. used ruthenium nanoparticles supported on carbon (Ru / C) to hydrogenate polyethylene into liquid alkanes with 8-45 carbon atoms after 16 hours of reaction at 200℃ and 2MPa hydrogen pressure. The mass yield of liquid alkanes was 45%, and the yield of gaseous products was >50%, with methane as the main product (JACS Au 2021, 1, 8-12). Molecular sieves and other catalysts with acid sites can greatly improve the selectivity of polyolefin degradation products, but they still suffer from poor catalytic activity and low degradation efficiency. Therefore, there is an urgent need to find a catalytic degradation method for polyolefin plastics that is efficient, highly selective, and yields products with high added value. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies in the degradation of polyolefin plastics, such as poor product selectivity, and to provide a catalytic degradation method for polyolefin plastics with low methane selectivity. The plastic degradation mixed catalyst in this invention exhibits high activity and good product selectivity, with a methane selectivity of less than 0.1% and a liquid product yield as high as 90%, wherein C5-C... 15 The selectivity of gasoline-related products exceeds 90%.
[0005] This invention provides a method for the catalytic degradation of polyolefin plastics with low methane selectivity, comprising the following steps: (1) A mixed catalyst is obtained by mixing M / Al2O3 and WO3, wherein the mass ratio of WO3 to M / Al2O3 is 0.1-30; (2) The mixed catalyst obtained in step (1) is mixed with polyolefin plastic, wherein M / Al2O3 and polyolefin plastic are in a mass ratio of 1:(1-20), and then transferred into a reactor filled with hydrogen. The temperature is raised and stirring is started. The temperature is continued to rise to the reaction temperature so that the polyolefin plastic is fully degraded. (3) After cooling to room temperature, the catalyst is recovered, an organic solvent is added to collect the liquid product, and the gaseous and liquid products are detected.
[0006] Preferably, in step (1), M is one or more of the precious metals platinum, ruthenium, palladium and rhodium or one or more of the non-precious metals nickel, copper, cobalt and zirconium.
[0007] Preferably, in step (1), the mixing method of the mixed catalyst is stirring, solid-phase grinding, or impregnation loading.
[0008] Preferably, in step (1), the loading of metal M in the mixed catalyst is 0.1-20 wt% based on the mass of Al2O3.
[0009] Preferably, in step (2), the polyolefin plastic is one or more of HDPE plastic raw material granules, LDPE plastic raw material granules, PP plastic raw material granules, and PS plastic raw material granules.
[0010] Preferably, in step (2), the hydrogen filling pressure is 0.1-5 MPa.
[0011] Preferably, in step (2), the temperature when stirring is started is 80-160℃.
[0012] Preferably, in step (2), the reaction temperature is 200-280℃.
[0013] Preferably, in step (2), the reaction time required for the complete degradation of polyolefin is 0.5-12h.
[0014] Preferably, in step (3), the gaseous products collected when the reaction ends and the temperature drops to room temperature include one or more of methane, ethane, propane, isobutane, and n-butane.
[0015] Preferably, in step (3), the specific process of recovering the catalyst is as follows: an organic solvent is added to the reaction system, the liquid product is dissolved in the solvent and then the solid and liquid are separated to obtain solid matter and liquid product. The solid matter is the mixture of the recovered catalyst and solid product.
[0016] Preferably, in step (3), the organic solvent is one or more of dichloromethane, chloroform, toluene, and ethyl acetate.
[0017] Preferably, in step (3), the liquid product is C5-C 16 n-Alkanes and C5-C 16 One or more of the isoalkanes.
[0018] The beneficial effects of this invention are: Using the polyolefin plastic degradation method provided by this invention, and employing M / Al2O3-WO3 (where M is one or more of noble metals such as platinum, ruthenium, palladium, and rhodium, or non-noble metals such as nickel, copper, cobalt, and zirconium) as a mixed catalyst, the efficiency of plastic degradation can be improved, achieving highly selective degradation of polyolefin plastics. Compared with previous methods, this invention has the advantage of simple catalyst synthesis; the catalyst can be prepared through physical mixing or impregnation, enabling large-scale preparation and application. Experimental results show that the polyolefin plastic degradation method provided by this invention, without the addition of solvents, successfully degrades polyolefin plastics after mixing the mixed catalyst with polyolefin plastics at a reaction temperature of 250°C for 4 hours. The conversion rate of polyolefins reaches 100%, the methane selectivity in the gaseous products is <0.1%, and the yield of liquid products is >90%, of which C5-C 15 Product selectivity > 90%. Attached Figure Description
[0019] Figure 1 The image shows a transmission electron microscope (TEM) image of the Ru / Al2O3 catalyst (2 wt% loading) in Example 1.
[0020] Figure 2 The graph shows the conversion rate of polyolefin plastic degradation and the composition of the resulting gaseous products in Examples 1-4 and Comparative Examples 1-3.
[0021] Figure 3 The graph shows the gas, liquid, and solid yields of polyolefin plastic degradation in Examples 1-4 and Comparative Examples 1-3.
[0022] Figure 4 The above are gas chromatograms of the gaseous products obtained in Examples 1-4 and Comparative Example 2.
[0023] Figure 5 The total ion chromatograms of the liquid products obtained in Examples 1, 3 and Comparative Example 2 are obtained by gas chromatography-mass spectrometry. Detailed Implementation
[0024] The following detailed description of a method for catalytic degradation of polyolefin plastics with low methane selectivity provided by the present invention, in conjunction with embodiments, is provided, but the implementation and protection scope of the present invention are not limited thereto.
[0025] Example 1 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 0.01 g WO3 into a reactor, grind and mix them evenly, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0026] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 4.8%, and the methane yield was 3.5%. The liquid product was collected and separated by adding dichloromethane as solvent. The liquid product was analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and 5 As shown, the yield of the liquid product was 55.0%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) was 40.2%.
[0027] Example 2 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 0.5 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0028] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 3.9%, and the methane yield was 0.09%. The liquid product was collected and separated by adding dichloromethane as solvent. The liquid product was analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and5 As shown, the yield of the liquid product was 96.1%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) is 0.
[0029] Example 3 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 1.0 g WO3 into a reactor, stir and mix evenly, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0030] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 4.7%, and the methane yield was 0.07%. The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and 5 As shown, the yield of the liquid product was 95.3%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) is 0.
[0031] Example 4 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 2.0 g WO3 into a reactor, stir and mix evenly, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0032] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 4.3%, and the methane yield was 0.07%. The liquid product was collected and separated by adding dichloromethane as solvent. The liquid product was analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and 5 As shown, the yield of the liquid product was 95.7%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) is 0.
[0033] Example 5 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 3.0 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 200℃, and react at 200℃ for 4 h.
[0034] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 4.
[0035] Example 6 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 0.1 wt%) and 0.1 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 1 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 220℃, and react at 220℃ for 4 h.
[0036] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 1.
[0037] Example 7 Weigh 0.1 g of Ni / Al2O3 catalyst (based on the mass of Al2O3, with a Ru loading of 20 wt%) and 0.1 g of WO3 into a reactor, mix them evenly by grinding, add 1.0 g of low-density polyethylene (LDPE) powder, fill with 0.1 MPa of hydrogen gas, heat to 130 °C and start stirring, continue heating to 220 °C, and react at 220 °C for 4 h.
[0038] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 1.
[0039] Example 8 Weigh 1.0 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 0.5 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 5 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0040] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 2.
[0041] Example 9 Weigh 0.05 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) and 0.5 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 4 h.
[0042] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 2.
[0043] Example 10 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 10 wt%) and 0.5 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 130℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 0.5 h.
[0044] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 2.
[0045] Example 11 Weigh 0.1 g Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 0.1 wt%) and 0.5 g WO3 into a reactor, mix them evenly by grinding, add 1.0 g low-density polyethylene (LDPE) powder, fill with 3 MPa hydrogen gas, heat to 160℃ and start stirring, continue to heat to 250℃, and react at 250℃ for 12 h.
[0046] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 2.
[0047] Example 12 Weigh 0.1 g of Pt / Al2O3 catalyst (based on the mass of Al2O3, with a Pt loading of 3wt%) and 1.0 g of WO3 into a reactor, stir until homogeneous, add 1.0 g of low-density polyethylene (LDPE) powder, fill with 3 MPa of hydrogen gas, heat to 80°C and start stirring, continue heating to 280°C, and react at 280°C for 4 h.
[0048] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 3.
[0049] Example 13 Weigh 0.1 g of Pd / Al2O3 catalyst (based on the mass of Al2O3, with a Pd loading of 1 wt%) and 0.5 g of WO3 into a reactor, grind and mix them evenly, add 1.0 g of high-density polyethylene (HDPE) powder, fill with 2 MPa of hydrogen gas, heat to 130℃ and start stirring, continue to heat to 280℃, and react at 280℃ for 2 h.
[0050] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding chloroform as a solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing, as in Example 2.
[0051] Example 14 Weigh 1.0 g of Al2O3 into a beaker and simultaneously load Ru and WO3 using a one-step impregnation method (based on the mass of Al2O3, the Ru loading is 1 wt% and the WO3 loading is 10 wt%). Add 2.0 g of polypropylene (PP) powder and stir until homogeneous. Fill with 2 MPa of hydrogen gas, heat to 110°C and start stirring. Continue heating to 260°C and react at 260°C for 5 h.
[0052] After the reaction was completed, the temperature was lowered to room temperature. The gaseous products were collected and qualitatively and quantitatively analyzed by GC (gas chromatography). The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed by GC-MS (gas chromatography-mass spectrometry). The solid products were quantitatively analyzed by weighing method, as in Example 1.
[0053] Comparative Example 1 Weigh 1.0 g of WO3 catalyst into a reactor, add 1.0 g of low-density polyethylene (LDPE) powder and stir until homogeneous, fill with 3 MPa of hydrogen gas, and react at 250℃ for 4 h.
[0054] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 0.6%. The liquid product was collected and separated by adding dichloromethane as solvent, and analyzed by GC-MS (gas chromatography-mass spectrometry). See attached figure. Figure 3 and 5 As shown, the yield of the liquid product was 6.0%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) was 93.4%.
[0055] Comparative Example 2 Weigh 0.1 g of Ru / WO3 catalyst (based on the mass of WO3, with a Ru loading of 2 wt%) into a reactor, add 1.0 g of low-density polyethylene (LDPE) powder and stir until homogeneous, fill with 3 MPa of hydrogen gas, and react at 250 °C for 4 h.
[0056] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 26.7%, and the methane yield was 23.9%. The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and 5As shown, the yield of the liquid product was 63.2%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) was 10.1%.
[0057] Comparative Example 3 Weigh 0.1 g of Ru / Al2O3 catalyst (based on the mass of Al2O3, with Ru loading of 2wt%) into a reactor, add 1.0 g of low-density polyethylene (LDPE) powder and stir until homogeneous, fill with 3 MPa of hydrogen gas, and react at 250℃ for 4 h.
[0058] After the reaction was complete, the mixture was cooled to room temperature, and the gaseous products were collected. Qualitative and quantitative analysis of the products was then performed using gas chromatography (GC), as shown in the attached figure. Figure 4 and 2 As shown, the gaseous product yield was 20.8%, and the methane yield was 17.6%. The liquid products were collected and separated by adding dichloromethane as solvent. The liquid products were analyzed using GC-MS (gas chromatography-mass spectrometry), as shown in the attached figure. Figure 3 and 5 As shown, the yield of the liquid product was 79.2%, and the solid product was quantitatively analyzed by gravimetric method, as shown in the attached figure. Figure 3 As shown, the yield of solid product (unconverted polyolefin plastic) is 0.
[0059] In summary, the beneficial effects of this invention are as follows: Using the polyolefin plastic degradation method provided by this invention, and employing M / Al2O3-WO3 (where M is one or more of noble metals such as platinum, ruthenium, palladium, and rhodium, or non-noble metals such as nickel, copper, cobalt, and zirconium) as a mixed catalyst, the efficiency of plastic degradation can be improved, achieving highly selective degradation of polyolefin plastics. Compared with previous methods, this invention has the advantage of simple catalyst synthesis; the catalyst can be prepared through physical mixing or impregnation, enabling large-scale preparation and application. Experimental results show that the polyolefin plastic degradation method provided by this invention, without the addition of solvents, successfully degrades polyolefin plastics after mixing the mixed catalyst with polyolefin plastics at a reaction temperature of 250°C for 4 hours. The conversion rate of polyolefins reaches 100%, and the methane selectivity in the gaseous products is <0.1% (see appendix). Figure 2 and Figure 4 Liquid product yield >90% (see appendix) Figure 3 ), of which C5-C 15 Product selectivity > 90% (see appendix) Figure 5 ).
[0060] The above description is merely a preferred embodiment of the present invention and is only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A method for catalytic degradation of polyolefin plastics with low methane selectivity, characterized in that, Includes the following steps: (1) Mix M / Al2O3 and WO3 to obtain a mixed catalyst, wherein the mass ratio of WO3 to M / Al2O3 is 0.1-30; (2) Mix the mixed catalyst described in step (1) with polyolefin plastic, wherein M / Al2O3 and polyolefin plastic are in a mass ratio of 1:(1-20), transfer it into a reaction vessel, fill it with hydrogen, heat up and start stirring, and continue to heat up to the reaction temperature so that the polyolefin plastic is fully degraded. (3) After cooling to room temperature, the catalyst is recovered, and an organic solvent is added to collect the liquid product. The gas and liquid products are then detected.
2. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (1), M is one or more of the precious metals platinum, ruthenium, palladium and rhodium or one or more of the non-precious metals nickel, copper, cobalt and zirconium.
3. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (1), the mixing method of the mixed catalyst is stirring, solid-phase grinding, and impregnation loading.
4. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (1), the loading of metal M in the mixed catalyst is 0.1-20 wt% based on the mass of Al2O3.
5. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (2), the polyolefin plastic is one or more of HDPE plastic raw material granules, LDPE plastic raw material granules, PP plastic raw material granules, and PS plastic raw material granules.
6. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (2), the hydrogen filling pressure is 0.1-5 MPa; the temperature when stirring is turned on is 80-160℃; the reaction temperature is 200-280℃; and the reaction time required for the polyolefin to fully degrade is 0.5-12h.
7. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (3), the gaseous products collected when the reaction ends and the temperature drops to room temperature include one or more of methane, ethane, propane, isobutane, and n-butane.
8. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (3), the specific process of recovering the catalyst is as follows: an organic solvent is added to the reaction system, the liquid product is dissolved in the organic solvent and then the solid and liquid are separated to obtain solid matter and liquid product, wherein the solid matter is a mixture of the recovered catalyst and solid product.
9. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (3), the organic solvent is one or more of dichloromethane, chloroform, toluene, and ethyl acetate.
10. The method for catalytic degradation of polyolefin plastics with low methane selectivity according to claim 1, characterized in that, In step (3), the liquid product is C5-C. 16 n-Alkanes and C5-C 16 One or more of the isoalkanes.