Method for catalytic degradation of polypropylene
By using a platinum catalyst supported on MCM-22 molecular sieve to catalytically degrade polypropylene in a hydrogen atmosphere, the problem of low degradation efficiency in existing technologies has been solved, achieving efficient conversion into high-value alkanes and improving resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIAXING UNIV
- Filing Date
- 2026-01-09
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies are insufficient for the efficient catalytic degradation of polypropylene, resulting in the formation of low-value methane from numerous branched structures, leading to low degradation efficiency and low resource utilization.
Platinum supported on MCM-22 molecular sieves was used as a catalyst for catalytic degradation in a hydrogen atmosphere. By controlling catalytic conditions such as temperature, pressure and time, the efficient conversion into high-value C4~C10 alkanes was achieved.
The method achieves efficient degradation of polypropylene with a conversion rate of 95.0%, and the C4-C10 alkane selectivity in the product reaches 98.9%, with almost no methane generation, thus improving the utilization value of resources.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polypropylene degradation technology, and more particularly to a method for catalytic degradation of polypropylene. Background Technology
[0002] In recent years, global plastic production has continued to rise, reaching 430.9 million tons in 2024, according to statistics. Of this, only 9.5% of waste plastics can be recycled mechanically, and only 0.1% can be recycled chemically. The vast majority of waste plastics can only be disposed of through landfill or incineration, which not only causes serious environmental pollution but also leads to a significant waste of resources. Therefore, researching the controllable chemical recycling of waste plastics to achieve resource recovery and recycling is of great research significance.
[0003] Polyethylene (PE) and polypropylene (PP) are the two most commonly used plastics in daily life, accounting for approximately 60% of total plastic production. PE and PP have stable alkane structures and are not easily degraded by chemical methods. In recent years, there has been extensive research on the catalytic cracking of PE. For example, Duan et al. used a sheet-like ZSM-5 molecular sieve to convert low-density polyethylene (LDPE) into C1-C7 alkanes at 280°C in a hydrogen atmosphere, achieving a yield of 74.6%; Wang et al. used a Beta molecular sieve to convert LPE into C5-C9 alkanes at 250°C in a hydrogen atmosphere, achieving a yield of 89.5%. However, research on the catalytic cracking of polypropylene is relatively limited. This is because polypropylene has a large number of branched chains, which easily generate low-value methane during catalytic cracking. For example, Rorrer et al. used a Ru / C catalyst to catalytically crack polypropylene, inevitably generating a large amount of methane in the products, resulting in a liquid yield of only 68%.
[0004] The numerous branched chains in polypropylene facilitate the formation of more alkane isomerization products, which can improve the anti-knock properties of gasoline and the low-temperature fluidity and oxidation stability of lubricating oils. Therefore, developing methods to crack polypropylene into high-value alkanes is of great significance. Summary of the Invention
[0005] The purpose of this invention is to provide a method for the catalytic degradation of polypropylene, addressing the shortcomings of existing technologies.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for the catalytic degradation of polypropylene, in which polypropylene and a catalyst are mixed in hydrogen gas and then subjected to catalytic degradation. The catalyst is a supported catalyst, the support for which is MCM-22 molecular sieve, and the active component of the supported catalyst is platinum.
[0007] Preferably, the mass of the active component in the supported catalyst is 0.5% of the support.
[0008] Preferably, the hydrogen pressure is 3-4 MPa, the catalytic degradation temperature is 270-280°C, and the catalytic degradation time is 4-10 h.
[0009] Preferably, the method for preparing the supported catalyst includes the following steps: 1) The MCM-22 molecular sieve was impregnated in a salt solution of the active component to obtain a catalyst precursor; 2) The catalyst precursor is calcined and reduced sequentially to obtain the supported catalyst.
[0010] Preferably, the calcination in step 2) is carried out in air at a temperature of 400°C for 4 hours.
[0011] Preferably, the reduction in step 2) is carried out in a hydrogen atmosphere at a temperature of 400°C for 4 hours.
[0012] Preferably, the MCM-22 molecular sieve is a hydrogen-form MCM-22 molecular sieve with a silica-to-alumina ratio of 13.9.
[0013] Preferably, the mass ratio of polypropylene to catalyst is 20:1.
[0014] Preferably, the catalyst can be reused after the catalytic degradation is completed.
[0015] The beneficial effects of this invention are: This invention uses MCM-22 molecular sieve-supported active components as a catalyst. By controlling the specific conditions of catalytic degradation, it achieves highly efficient degradation of polypropylene. The degradation process produces almost no methane, and the conversion rate of polypropylene can reach 95.0%. The product contains C4~C4 molecules. 10 The selectivity of alkanes can reach 98.9%, which greatly increases the added value of the product and is of great significance for the resource utilization of waste plastics. Detailed Implementation
[0016] This invention provides a method for the catalytic degradation of polypropylene, in which polypropylene and a catalyst are mixed in hydrogen gas and then subjected to catalytic degradation. The catalyst is a supported catalyst, the support for which is MCM-22 molecular sieve, and the active component of the supported catalyst is platinum.
[0017] In this invention, the mass of the active component in the supported catalyst is preferably 0.5% of the support.
[0018] In this invention, the pressure of the hydrogen gas is preferably 3-4 MPa, more preferably 3.2-3.8 MPa, and even more preferably 3.5 MPa; the temperature of the catalytic degradation is preferably 270-280℃, more preferably 272-278℃, and even more preferably 275℃; the time of the catalytic degradation is preferably 4-10 h, more preferably 5-8 h, and even more preferably 6-7 h.
[0019] In this invention, the method for preparing the supported catalyst preferably includes the following steps: 1) The MCM-22 molecular sieve was impregnated in a salt solution of the active component to obtain a catalyst precursor; 2) The catalyst precursor is calcined and reduced sequentially to obtain the supported catalyst.
[0020] In this invention, the salt solution of the active component in step 1) preferably includes a platinum nitrate solution and / or a chloroplatinic acid solution.
[0021] In this invention, the calcination in step 2) is preferably carried out in air, the calcination temperature is preferably 400°C, and the calcination time is preferably 4 hours.
[0022] In this invention, the reduction in step 2) is preferably carried out in a hydrogen atmosphere, the reduction temperature is preferably 400°C, and the reduction time is preferably 4 hours.
[0023] In this invention, the MCM-22 molecular sieve is preferably a hydrogen-form MCM-22 molecular sieve, and the silica-alumina ratio of the hydrogen-form MCM-22 molecular sieve is preferably 13.9.
[0024] In this invention, the preferred mass ratio of polypropylene to catalyst is 20:1.
[0025] In this invention, the catalytic degradation is preferably carried out by stirring, and the stirring speed is preferably 500~1000 rpm, more preferably 600~900 rpm, and even more preferably 700~800 rpm.
[0026] In this invention, after the catalytic degradation is completed, the catalyst is preferably reusable.
[0027] In this invention, the preferred method for reusing the catalyst is to calcine the used catalyst. The preferred roasting temperature is 500℃, and the preferred roasting time is 4 hours.
[0028] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0029] The polypropylene used in the embodiments and comparative examples of this invention is commercial polypropylene (melt index 4 g / 10 min, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.).
[0030] Example 1
[0031] 4.7475 g of hydrogen-form MCM-22 molecular sieve with a silica-to-alumina ratio of 13.9 was placed in a round-bottom flask, and deionized water was added to cover the sieve. Stirring was started at 300 rpm, and 3.14 g of chloroplatinic acid solution with a concentration of 7.5 mg / mL (calculated as platinum) was added during stirring. Stirring was continued at 300 rpm for 4 h to obtain the catalyst precursor. The catalyst precursor was dried by rotary evaporation and calcined at 400 °C for 4 h. After calcination, it was ground and reduced at 400 °C under a hydrogen atmosphere with a flow rate of 100 SCCM for 4 h. After reduction, it was cooled to room temperature to obtain the supported catalyst (the mass of the active component Pt was 0.5% of the support MCM-22 molecular sieve), labeled as Pt / MCM-22.
[0032] 0.75g of catalyst Pt / MCM-22 and 15g of polypropylene were placed in a reactor, sealed, and purged three times with nitrogen, followed by five times with hydrogen to maintain a hydrogen atmosphere. The reactor was heated to 150℃, stirred at 800rpm, and the temperature was further increased to 275℃. Catalytic degradation was carried out at 275℃ and a hydrogen pressure of 3MPa for 4 hours. After the reaction, stirring was stopped and the mixture was allowed to cool to room temperature. The top pipe of the reactor was connected to a gas collection bag to release and collect the gaseous products until the pressure reading reached atmospheric pressure. The reactor was then placed in an ice-water mixture. When the temperature inside the reactor dropped to 9.2℃, the reactor was opened, and the solid and liquid products were obtained by filtration. The solid product was a mixture of undegraded polypropylene and the supported catalyst, and the liquid product was C4~C6. 10 Alkanes. The solid product was washed with dichloromethane, dried, and then placed in a muffle furnace and calcined at 500°C for 4 hours. After cooling to room temperature, it was ground to obtain a regenerated catalyst, which can be reused.
[0033] Gaseous products were analyzed using a Shimadzu gas chromatograph (GC-2014AFSC) equipped with a flame ionization detector (FID) and a PLOT column (30m × 0.32mm × 10μm), and the component contents were calculated using the external standard method. Liquid products were analyzed using an Agilent gas chromatograph (Agilent 7890B) equipped with a flame ionization detector (FID) and an HP-5 column (30m × 0.32mm × 0.25μm), and the component contents were calculated using the internal standard method.
[0034] In this embodiment, the conversion rate of polypropylene was 92.3%, and the product was C4~C4. 10The selectivity for alkanes was 98.9%, and the selectivity for methane was 0.003%.
[0035] Example 2
[0036] The difference from Example 1 is that the catalytic degradation temperature is 270°C.
[0037] In this embodiment, the conversion rate of polypropylene was 86.9%, and the product was C4~C4. 10 The selectivity for alkanes was 98.8%, and the selectivity for methane was 0.002%.
[0038] Example 3
[0039] The difference from Example 1 is that the catalytic degradation temperature is 280°C.
[0040] In this embodiment, the conversion rate of polypropylene was 86.9%, and the product was C4~C4. 10 The selectivity for alkanes was 98.5%, and the selectivity for methane was 0.003%.
[0041] Example 4
[0042] The difference from Example 1 is that the catalytic degradation time is 10 hours.
[0043] In this embodiment, the conversion rate of polypropylene was 92.9%, and the product was C4~C4. 10 The selectivity for alkanes was 97.7%, and the selectivity for methane was 0.005%.
[0044] Example 5
[0045] The difference from Example 1 is that the hydrogen pressure for catalytic degradation is 3.8 MPa.
[0046] In this embodiment, the conversion rate of polypropylene was 93.7%, and the product was C4~C4. 10 The selectivity for alkanes was 98.2%, and the selectivity for methane was 0.009%.
[0047] Example 6
[0048] The difference from Example 1 is that the hydrogen pressure for catalytic degradation is 4 MPa.
[0049] In this embodiment, the conversion rate of polypropylene is 95.0%, and the product is C4~C4. 10 The selectivity for alkanes was 97.8%, and the selectivity for methane was 0.002%.
[0050] The catalytic degradation conditions and reaction evaluations of Examples 1-6 are shown in Table 1.
[0051] Comparative Example 1
[0052] The difference from Example 1 is that the catalytic degradation temperature is 260°C.
[0053] In this comparative example, the conversion rate of polypropylene was 72.6%, and the product was C4~C6. 10 The selectivity for alkanes was 97.4%, and the selectivity for methane was 0.007%.
[0054] Comparative Example 2
[0055] The difference from Example 1 is that the hydrogen pressure for catalytic degradation is 2.5 MPa.
[0056] In this comparative example, the conversion rate of polypropylene was 68.7%, and the product was C4~C4. 10 The selectivity for alkanes was 98.1%, and the selectivity for methane was 0.001%.
[0057] Comparative Example 3
[0058] The difference from Example 3 is that the catalytic degradation time is 1 hour.
[0059] In this comparative example, the conversion rate of polypropylene was 50.1%, and the product was C4~C4. 10 The selectivity for alkanes was 94.3%, and the selectivity for methane was 0.003%.
[0060] The catalytic degradation conditions and reaction evaluations for Comparative Examples 1-3 are shown in Table 1.
[0061] Comparative Example 4
[0062] The difference from Example 1 is as follows: 8.9775g of hydrogen-form MCM-22 molecular sieve with a silicon-to-aluminum ratio of 13.9 was placed in a round-bottom flask, and deionized water was added to cover the molecular sieve. Stirring was started at 300 rpm, and 5.985g of palladium nitrate solution with a concentration of 7.5 mg / mL (calculated as palladium) was added during stirring. Stirring was continued at 300 rpm for 4 hours to obtain the catalyst precursor. The catalyst precursor was dried by rotary evaporation and calcined at 400°C for 4 hours. After calcination, it was ground and reduced at 400°C under a hydrogen atmosphere with a flow rate of 100 SCCM for 4 hours. After reduction, it was cooled to room temperature to obtain a supported catalyst (the mass of the active component Pd was 0.5% of the support MCM-22 molecular sieve), labeled as Pd / MCM-22.
[0063] In this embodiment, the conversion rate of polypropylene was 76.3%, and the product was C4~C4. 10 The selectivity for alkanes was 97.1%, and the selectivity for methane was 0.0097%.
[0064] Comparative Example 5
[0065] The difference from Example 1 is as follows: 5.0233 g of hydrogen-form MCM-22 molecular sieve with a silicon-to-aluminum ratio of 13.9 was placed in a round-bottom flask, and deionized water was added to cover the molecular sieve. Stirring was started at 300 rpm, and during stirring, 33.49 g of ruthenium trichloride solution with a concentration of 7.5 mg / mL (calculated as ruthenium) was added. Stirring was then continued at 300 rpm for 4 h to obtain the catalyst precursor. The catalyst precursor was dried by rotary evaporation and calcined at 400 °C for 4 h. After calcination, it was ground and reduced at 450 °C under a hydrogen atmosphere with a flow rate of 100 SCCM for 4 h. After reduction, it was cooled to room temperature to obtain the supported catalyst (the mass of the active component Ru was 5% of the support MCM-22 molecular sieve), labeled as Ru / MCM-22.
[0066] In this embodiment, the conversion rate of polypropylene is 77.5%, and the product is C4~C4. 10 The selectivity for alkanes was 97.5%, and the selectivity for methane was 0.78%.
[0067] Comparative Example 6
[0068] The difference from Example 1 is as follows: 5.4502 g of hydrogen-form MCM-22 molecular sieve with a silicon-to-aluminum ratio of 13.9 was placed in a round-bottom flask, and deionized water was added to cover the molecular sieve. Stirring was started at 300 rpm, and 36.33 g of nickel nitrate solution with a concentration of 7.5 mg / mL (calculated as nickel) was added during stirring. Stirring was continued at 300 rpm for 4 hours to obtain the catalyst precursor. The catalyst precursor was dried by rotary evaporation and calcined at 400 °C for 4 hours. After calcination, it was ground and reduced at 400 °C under a hydrogen atmosphere with a flow rate of 100 SCCM for 4 hours. After reduction, it was cooled to room temperature to obtain a supported catalyst (the mass of the active component Ni was 5% of the support MCM-22 molecular sieve), labeled as Ni / MCM-22.
[0069] In this embodiment, the conversion rate of polypropylene was 78.5%, and the product was C4~C4. 10 The selectivity for alkanes was 97.7%, and the selectivity for methane was 0.0618%.
[0070] The catalytic degradation conditions and reaction evaluations for Comparative Examples 4-6 are shown in Table 2.
[0071] Table 1. Catalytic degradation conditions and reaction evaluation of Examples 1-6 and Comparative Examples 1-3
[0072] Table 2 Catalytic degradation conditions and reaction evaluation of comparative examples 4-6
[0073] As can be seen from the above examples and comparative examples, the present invention provides a method for catalytic degradation of polypropylene, using MCM-22 molecular sieve as a support and platinum as the active component of a supported catalyst. By reasonably controlling the specific conditions of catalytic degradation, the method achieves efficient degradation of polypropylene, and the degradation process produces almost no methane, thereby improving the degradation efficiency of polypropylene and the added value of the product.
[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for catalytic degradation of polypropylene, characterized in that, Polypropylene and the catalyst are mixed in hydrogen gas and then subjected to catalytic degradation. The catalyst is a supported catalyst, the support for which is MCM-22 molecular sieve, and the active component of the supported catalyst is platinum.
2. The method for catalytic degradation of polypropylene according to claim 1, characterized in that, The active component in the supported catalyst is 0.5% of the support.
3. The method for catalytic degradation of polypropylene according to claim 1 or 2, characterized in that, The hydrogen pressure is 3~4 MPa, the catalytic degradation temperature is 270~280℃, and the catalytic degradation time is 4~10 h.
4. The method for catalytic degradation of polypropylene according to claim 3, characterized in that, The method for preparing the supported catalyst includes the following steps: 1) The MCM-22 molecular sieve was impregnated in a salt solution of the active component to obtain a catalyst precursor; 2) The catalyst precursor is calcined and reduced sequentially to obtain the supported catalyst.
5. The method for catalytic degradation of polypropylene according to claim 4, characterized in that, Step 2) The calcination is carried out in air at a temperature of 400°C for 4 hours.
6. The method for catalytic degradation of polypropylene according to claim 5, characterized in that, Step 2) The reduction is carried out in a hydrogen atmosphere at a temperature of 400°C for 4 hours.
7. The method for catalytic degradation of polypropylene according to claim 1 or 6, characterized in that, The MCM-22 molecular sieve is a hydrogen-form MCM-22 molecular sieve with a silica-to-alumina ratio of 13.
9.
8. The method for catalytic degradation of polypropylene according to claim 7, characterized in that, The mass ratio of polypropylene to catalyst is 20:
1.
9. The method for catalytic degradation of polypropylene according to claim 8, characterized in that, After the catalytic degradation is completed, the catalyst can be reused.