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CN-121990900-A - Method for producing benzoic acid by degrading polystyrene by photo-thermal synergistic catalyst and application thereof

CN121990900ACN 121990900 ACN121990900 ACN 121990900ACN-121990900-A

Abstract

The invention discloses a method for producing benzoic acid by degrading polystyrene by a photo-thermal synergistic catalyst and application thereof, belonging to the technical field of waste plastic recycling, wherein the method comprises the steps of constructing a reaction system comprising polystyrene, the photo-thermal synergistic catalyst and a solvent, and carrying out depolymerization reaction under the condition of illumination and heating to prepare the benzoic acid; the photo-thermal synergistic catalyst is sulfur-doped graphite phase carbon nitride rich in nitrogen vacancies, and is prepared by mixing and dissolving urea and thiourea according to a mass ratio of 0.5-9:1, evaporating and crystallizing to obtain a precursor mixture, heating and calcining the precursor mixture in an air atmosphere to obtain a sulfur-doped carbon nitride precursor, performing heat treatment on the sulfur-doped carbon nitride precursor in an ammonia atmosphere, and introducing nitrogen vacancy defects to obtain the photo-thermal synergistic catalyst. The method has the advantages of mild conditions, high catalytic efficiency of the catalyst, high polystyrene conversion efficiency and environmental protection.

Inventors

  • LIU YUE
  • FU SIQI
  • WANG YUXIONG
  • WU ZHONGBIAO

Assignees

  • 浙江大学

Dates

Publication Date
20260508
Application Date
20260408

Claims (9)

  1. 1. The method for producing the benzoic acid by degrading the polystyrene by using the photo-thermal synergistic catalyst is characterized by comprising the following steps of: constructing a reaction system comprising polystyrene, a photo-thermal synergistic catalyst and a solvent, and carrying out depolymerization reaction under the condition of illumination and heating to prepare benzoic acid; The photo-thermal synergistic catalyst is sulfur-doped graphite phase carbon nitride rich in nitrogen vacancies, and is prepared by mixing and dissolving urea and thiourea according to a mass ratio of 0.5-9:1, evaporating and crystallizing to obtain a precursor mixture, heating and calcining the precursor mixture in an air atmosphere to obtain a sulfur-doped carbon nitride precursor, performing heat treatment on the sulfur-doped carbon nitride precursor in an ammonia atmosphere, and introducing nitrogen vacancy defects to obtain the photo-thermal synergistic catalyst.
  2. 2. The method for producing benzoic acid by degrading polystyrene by using a photo-thermal synergistic catalyst according to claim 1, wherein the mass ratio of the polystyrene to the photo-thermal synergistic catalyst is 1:0.1-2.
  3. 3. The method for producing benzoic acid by degrading polystyrene with a photo-thermal co-catalyst according to claim 1, wherein the solvent comprises acetonitrile, acetone or water.
  4. 4. The method for producing benzoic acid by degrading polystyrene by using the photo-thermal synergistic catalyst according to claim 1 is characterized in that the illumination condition is that the light source wavelength is 280-2500 nm, the light intensity is 500-1000 mW/cm 2 , the heating condition is that the reaction temperature is 90-210 ℃, and the reaction time is 1-24 h.
  5. 5. The method for producing benzoic acid by degrading polystyrene with a photo-thermal synergistic catalyst according to claim 1, wherein the depolymerization reaction is carried out in an oxidizing atmosphere.
  6. 6. The method for producing benzoic acid by degrading polystyrene by using a photo-thermal synergistic catalyst according to claim 1, wherein the mass ratio of urea to thiourea is 0.5-5:1 in the preparation process of the photo-thermal synergistic catalyst.
  7. 7. The method for producing benzoic acid by degrading polystyrene by using a photo-thermal synergistic catalyst according to claim 1, wherein the condition of heating and calcining the precursor mixture in an air atmosphere is 450-550 ℃, and the heat preservation time is 2-4 hours.
  8. 8. The method for producing benzoic acid by degrading polystyrene with a photo-thermal synergistic catalyst according to claim 1, wherein the condition of heat treatment of sulfur-doped carbon nitride precursor in ammonia atmosphere is 450-550 ℃, the heat preservation time is 1-4 h, and the ammonia volume concentration is 10-80 vol%.
  9. 9. The use of the method for producing benzoic acid by degrading polystyrene with a photo-thermal co-catalyst according to any one of claims 1-8 in the treatment of waste polystyrene.

Description

Method for producing benzoic acid by degrading polystyrene by photo-thermal synergistic catalyst and application thereof Technical Field The invention belongs to the technical field of recycling of waste plastics, and particularly relates to a method for producing benzoic acid by degrading polystyrene by using a photo-thermal synergistic catalyst and application of the method. Background Polystyrene (PS) is one of the most widely used plastics at present, has excellent properties of light weight, heat insulation, corrosion resistance and the like, and is mainly applied to the fields of packaging materials, disposable tableware, electronic product shells, building materials and the like. However, polystyrene waste is difficult to degrade naturally, can exist in natural environments for hundreds of years, affect ecological balance, and present health risks. Therefore, the technology for treating the polystyrene waste with high efficiency and cleanliness is developed, the resource utilization of the polystyrene waste is realized, and the environmental significance and the economic value are important. At present, the polystyrene waste is mainly treated by three modes of landfill, incineration and mechanical recovery. The landfill treatment occupies a large amount of land resources, and the polystyrene has stable chemical property, hardly degrades under natural conditions, and can cause long-term potential pollution. Although part of heat energy can be recovered in the incineration treatment, a large amount of carbon dioxide, polycyclic aromatic hydrocarbon, dioxin and other toxic and harmful gases can be generated in the combustion process, so that serious secondary pollution is caused. Mechanical recycling is to reprocess waste plastics into plastic products by means of melting and re-granulating, but the process often leads to the reduction of the molecular weight of polystyrene, the degradation of mechanical properties, the degradation of the polystyrene, and the final waste treatment after multiple cycles. Therefore, the traditional treatment mode is difficult to realize green, efficient and resource utilization of the polystyrene waste. Chemical recycling techniques are considered ideal ways to achieve recycling of waste plastics by depolymerizing the waste plastics into monomers or converting them into high value-added chemicals. Polystyrene is a linear high molecular polymer formed from styrene monomers by polyaddition reactions, and generally has a molecular weight between tens of thousands and hundreds of thousands. The polystyrene molecular chain contains a large number of benzene ring side groups, so that the polystyrene molecular chain has higher chemical stability and thermal stability. At present, some researches realize the recycling and high-value of polystyrene, for example, chinese patent literature with publication number of CN121342644A discloses a method for degrading polystyrene plastic based on nano MnO 2 photocatalytic ozone oxidation and upgrading and recycling the polystyrene plastic into benzoic acid, which mixes PS plastic fragments with nano MnO 2 and an organic solvent, and then simultaneously introduces ozone into a reaction system at normal temperature and normal pressure and irradiates the reaction system with light. Through the synergistic catalysis of light and ozone, the molecular chain of PS plastic can be efficiently and selectively broken and oxidized, and finally the PS plastic is directionally converted into benzoic acid with high added value. The Chinese patent document with publication number CN120208744A discloses a method for preparing single benzene ring liquid chemicals by solvent-free hydrogenation degradation of polystyrene waste plastics based on a bifunctional catalyst, which takes Nb 2O5 as a carrier to load 1-3wt% of noble metal ruthenium for preparing the bifunctional catalyst, and the hydrogenation reaction is carried out under the solvent-free condition to efficiently degrade high molecular weight polystyrene into benzene, toluene, ethylbenzene and other single benzene ring liquid chemicals. However, the above method has problems of high energy consumption, high cost caused by the use of noble metal or ozone, and further improvement of conversion efficiency. The photo-thermal synergistic catalysis technology combines the advantages of photocatalysis and thermocatalysis, and provides a new idea for the efficient conversion of waste plastics. The core of the photo-thermal synergistic catalysis is that the photo-energy is converted into heat energy, so that the local temperature rise of the surface of the catalyst is realized, and the photo-generated carriers directly participate in the reaction, so that the reaction efficiency is obviously improved under the synergistic effect of the photo-generated carriers and the heat energy. However, the research on the degradation of polystyrene by the photo-thermal synergistic catalyst is insufficient at present, and