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CN-122010666-A - Polypropylene catalytic degradation method

CN122010666ACN 122010666 ACN122010666 ACN 122010666ACN-122010666-A

Abstract

The invention belongs to the technical field of polypropylene degradation, and provides a method for catalyzing and degrading polypropylene. The method for catalytic degradation of polypropylene comprises the steps of mixing polypropylene with a catalyst in hydrogen for catalytic degradation, wherein the catalyst is a supported catalyst, a carrier of the supported catalyst is an MCM-22 molecular sieve, and an active component of the supported catalyst is platinum. According to the invention, the MCM-22 molecular sieve loaded active component is used as a catalyst, and the high-efficiency degradation of polypropylene is realized by regulating and controlling the catalyst dosage and the specific conditions of catalytic degradation, almost no methane is generated in the degradation process, the conversion rate of polypropylene can reach 95.0%, the selectivity of C 4 ~C 10 alkane in the product can reach 98.9%, the added value of the product is greatly improved, and the method has important significance for recycling waste plastics.

Inventors

  • Zhu longfeng
  • XU JIAWEI
  • YANG YUHAN
  • HAN HUIJUAN
  • CAO XUEBO

Assignees

  • 嘉兴大学

Dates

Publication Date
20260512
Application Date
20260109

Claims (9)

  1. 1. A method for catalytic degradation of polypropylene is characterized in that polypropylene and a catalyst are mixed in hydrogen for catalytic degradation; the catalyst is a supported catalyst, the carrier of the supported catalyst is MCM-22 molecular sieve, and the active component of the supported catalyst is platinum.
  2. 2. The method for catalytic degradation of polypropylene according to claim 1, wherein the mass of active component in the supported catalyst is 0.5% of the carrier.
  3. 3. The method for catalytic degradation of polypropylene according to claim 1 or 2, wherein the pressure of the hydrogen is 3-4 mpa, the catalytic degradation temperature is 270-280 ℃, and the catalytic degradation time is 4-10 h.
  4. 4. A method of catalytic degradation of polypropylene according to claim 3, wherein the preparation of the supported catalyst comprises the steps of: 1) Impregnating an MCM-22 molecular sieve in a salt solution of an active component to obtain a catalyst precursor; 2) And (3) calcining and reducing the catalyst precursor in sequence to obtain the supported catalyst.
  5. 5. The method for catalytic degradation of polypropylene according to claim 4, wherein the calcination in step 2) is carried out in air at a temperature of 400 ℃ for a time of 4 hours.
  6. 6. The method for catalytic degradation of polypropylene according to claim 5, wherein the reduction in step 2) is carried out in a hydrogen atmosphere at a temperature of 400 ℃ for a time of 4 hours.
  7. 7. The method for catalytic degradation of polypropylene according to claim 1 or 6, wherein the MCM-22 molecular sieve is a hydrogen form MCM-22 molecular sieve, and the silicon to aluminum ratio of the hydrogen form MCM-22 molecular sieve is 13.9.
  8. 8. The method for catalytic degradation of polypropylene according to claim 7, wherein the mass ratio of polypropylene to catalyst is 20:1.
  9. 9. The method for catalytic degradation of polypropylene according to claim 8, wherein the catalyst is reusable after the catalytic degradation is completed.

Description

Polypropylene catalytic degradation method Technical Field The invention relates to the technical field of polypropylene degradation, in particular to a method for catalyzing and degrading polypropylene. Background In recent years, global plastic production has been continuously rising, and it has been counted that 4.309 million tons have been reached in 2024. Wherein, only 9.5% of the waste plastics can be recovered mechanically, 0.1% of the waste plastics can be recovered chemically, and most of the waste plastics can only be treated by landfill or incineration, which not only causes serious environmental pollution, but also causes a great amount of resource waste. Therefore, the controllable chemical recovery of waste plastics is researched, the plastic recycling and cyclic utilization are realized, and the method has very important research significance. Polyethylene and polypropylene are the two most commonly used plastics in everyday life, with yields of polyethylene and polypropylene being about 60% of the total plastics yield. Polyethylene and polypropylene have stable alkane structures and are not easy to degrade by chemical methods. In recent years, there have been a great deal of research on catalytic cracking of polyethylene, for example, duan et al used a platy ZSM-5 molecular sieve to convert low density polyethylene into C 1~C7 alkane under 280 ℃ hydrogen atmosphere in a yield of 74.6%, wang et al used Beta molecular sieve to convert low density polyethylene into C 5~C9 alkane under 250 ℃ hydrogen atmosphere in a yield of 89.5%. However, the research on the catalytic cracking of polypropylene is relatively less, because polypropylene has a large number of branched structures, and low-value methane is easy to generate in the catalytic cracking process. For example, rorrer et al use Ru/C catalysts to catalyze the cracking of polypropylene, and inevitably produce large amounts of methane in the product, resulting in liquid yields of the product of only 68%. The large number of branched chains in the polypropylene is favorable for generating more alkane isomerization products, and the alkane isomerization products can improve the antiknock performance of the gasoline and the low-temperature fluidity and oxidation stability of the lubricating oil. Therefore, it is of great importance to develop a process that is capable of cleaving polypropylene into high value alkanes. Disclosure of Invention The invention aims to provide a method for catalyzing and degrading polypropylene in order to overcome the defects in the prior art. In order to achieve the above object, the present invention provides the following technical solutions: the invention provides a method for catalyzing and degrading polypropylene, which comprises the steps of mixing polypropylene and a catalyst in hydrogen, and carrying out catalytic degradation; the catalyst is a supported catalyst, the carrier of the supported catalyst is MCM-22 molecular sieve, and the active component of the supported catalyst is platinum. Preferably, the mass of the active component in the supported catalyst is 0.5% of the carrier. Preferably, the pressure of the hydrogen is 3-4 MPa, the catalytic degradation temperature is 270-280 ℃, and the catalytic degradation time is 4-10 h. Preferably, the preparation method of the supported catalyst comprises the following steps: 1) Impregnating an MCM-22 molecular sieve in a salt solution of an active component to obtain a catalyst precursor; 2) And (3) calcining and reducing the catalyst precursor in sequence to obtain the supported catalyst. Preferably, the calcination in step 2) is carried out in air at a temperature of 400 ℃ for a period of 4 hours. Preferably, the reduction in step 2) is carried out in a hydrogen atmosphere at a temperature of 400 ℃ for a period of 4 hours. Preferably, the MCM-22 molecular sieve is a hydrogen type MCM-22 molecular sieve, and the silicon-aluminum ratio of the hydrogen type MCM-22 molecular sieve is 13.9. Preferably, the mass ratio of the polypropylene to the catalyst is 20:1. Preferably, after the catalytic degradation is finished, the catalyst can be reused. The invention has the beneficial effects that: According to the invention, the MCM-22 molecular sieve loaded active component is used as a catalyst, and the specific conditions of catalytic degradation are regulated to realize high-efficiency degradation of polypropylene, almost no methane is generated in the degradation process, the conversion rate of polypropylene can reach 95.0%, the selectivity of C 4~C10 alkane in the product can reach 98.9%, the added value of the product is greatly improved, and the method has important significance for recycling waste plastics. Detailed Description The invention provides a method for catalyzing and degrading polypropylene, which comprises the steps of mixing polypropylene and a catalyst in hydrogen, and carrying out catalytic degradation; the catalyst is a supported catalyst, the c