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CN-121974794-A - Method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst

CN121974794ACN 121974794 ACN121974794 ACN 121974794ACN-121974794-A

Abstract

The invention discloses a method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst, which comprises the steps of adding the waste high-molecular polymer and water into a reactor, carrying out oxidation reaction in an oxygen-containing atmosphere, cooling, collecting liquid products, and removing water to obtain small molecular acid, wherein the melting point of the waste high-molecular polymer is recorded as T m , and the temperature of the oxidation reaction is not lower than T m -20 ℃ and not higher than T m +50 ℃. The invention provides a method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst, which only needs water and oxygen, does not need catalyst, has low reaction temperature, can easily separate products and further convert the products into high-value chemicals such as glycol, diamine and the like, and provides a new green, nontoxic, economical and feasible path for plastic recovery.

Inventors

  • WANG YONG
  • GAO RUILIANG
  • MAO SHANJUN

Assignees

  • 浙江大学

Dates

Publication Date
20260505
Application Date
20251218

Claims (10)

  1. 1. The method for preparing the small molecular acid by oxidizing the waste high molecular polymer at a low temperature without a catalyst is characterized by comprising the following steps: Adding waste high molecular polymers and water into a reactor, performing oxidation reaction in an oxygen-containing atmosphere, cooling, collecting a liquid product, and removing water to obtain small molecular acid; The melting point of the waste high molecular polymer is recorded as T m , and the temperature of the oxidation reaction is not lower than T m -20 ℃ and not higher than T m +50 ℃.
  2. 2. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, which is characterized in that: the waste high molecular polymer is selected from one or more of waste polyolefin, waste polyester and waste polyurethane; the mass ratio of the waste high polymer to the water is 1 (6.5-50).
  3. 3. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, wherein the mass ratio of the waste high molecular polymer to water is 1 (12.5-25).
  4. 4. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, which is characterized in that: the atmosphere containing oxygen is selected from oxygen and/or air; in the atmosphere containing oxygen, the partial pressure of oxygen is 0.3-5.0 Mpa.
  5. 5. The method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst according to claim 1, wherein the oxygen partial pressure is 1.0-3.0 Mpa in the oxygen-containing atmosphere.
  6. 6. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, wherein the temperature of the oxidation reaction is not lower than T m and not higher than T m +10 ℃.
  7. 7. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, wherein H 2 O 2 is additionally added.
  8. 8. The method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst according to claim 7, wherein the addition amount of H 2 O 2 is 0.5-5.0% based on 100% of water volume.
  9. 9. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, wherein the time of the oxidation reaction is not less than 6 h.
  10. 10. The method for preparing small molecular acid by low-temperature oxidation of waste high molecular polymer without catalyst according to claim 1, wherein the time of the oxidation reaction is not less than 12 h.

Description

Method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst Technical Field The invention relates to the technical field of high polymer material recovery, in particular to a method for preparing small molecular acid by low-temperature oxidation of waste high polymer without a catalyst. Background Since the 50 s of the 20 th century, mass production and improper management of plastics has raised serious environmental and health concerns. The micro-plastics generated by the plastic waste penetrate into ecosystems such as arctic and deep sea, threaten human health, and possibly cause the damage of cancer incidence rate rise, abnormal reproductive system and the like. Polyethylene (PE) is almost one third of the global plastic yield, and natural degradation is extremely difficult due to its stable C (sp 3) -C (sp 3) bond structure. Although prior recovery techniques (e.g., pyrolysis, hydrocracking, hydrogenolysis, etc.) have been developed, the products are mostly complex mixtures of alkanes and alkenes. The process has the common problems of high energy consumption, low selectivity, high catalyst cost or easy deactivation, etc., so that the operation cost is high and the economic feasibility is limited. In addition, the resulting hydrocarbon mixture is often used as a conventional fuel, indirectly exacerbating carbon dioxide emissions. In comparison, upgrading PE to a recyclable high value-added chemical is more attractive. For example, PE oxidation recovery can produce high value dicarboxylic acids, but the prior art still faces the challenge of obtaining about 85% liquid product at 160℃under 1.5 MPa air conditions using Ru/TiO 2 catalyst (DOI: 10.1002/anie.202407510), and Wang et al use Co/MCM catalyst to degrade PE to dicarboxylic acids with carbon chain lengths of 10-20 in 125℃1 MPa oxygen (DOI: 10.1002/anie.202301340). However, such methods rely on expensive catalysts, saturated dibasic acids have low selectivity and difficult product separation, severely limiting their commercial application. Recently, the new technology, hydrothermal liquefaction, has been developed by Mura technology, london, and supercritical water (400 ℃ C./220 atm) has been used to convert waste polymers into hydrocarbon mixtures, such as naphtha, heavy resid, etc. However, the technology still has the defects of strict reaction conditions, high manufacturing cost of reaction equipment, low product selectivity, low added value and the like. Xu et al can obtain acetic acid and benzoic acid by subcritical hydrothermal treatment of polypropylene and polystyrene at 160 ℃, but the substrate can only be a polymer containing tertiary carbon (PP, PS) and the conversion and selectivity are significantly lower (DOI: 10.1021/acs.4c04449). In recent years, catalyst-free oxidation techniques based on micro-droplet reactions have been of great interest. The gas-liquid or water-oil interface of the droplets can form a unique reaction environment, triggering interface catalysis and spontaneous redox reactions, thereby accelerating the chemical process. Studies have shown that the droplet surface can generate an electric field (DOI: 10.1038/s 41586-025-08702-y) of up to 10 9 V/m, sufficient to extract electrons from OH-, generating hydroxyl radicals (. OH) and free electrons. At present, the technology is mainly used for organic synthesis, and related reports of degrading waste high polymer by utilizing a micro-droplet catalyst-free oxidation technology are not available. Disclosure of Invention Based on the method, the invention provides a method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst, which only needs water and oxygen, does not need catalyst, has low reaction temperature, can easily separate products and further convert the products into high-value chemicals such as glycol, diamine and the like, and provides a new green, nontoxic, economical and feasible path for plastic recovery. The specific technical scheme is as follows: A method for preparing small molecular acid by low-temperature oxidation of waste high-molecular polymer without catalyst comprises the following steps: Adding waste high molecular polymers and water into a reactor, performing oxidation reaction in an oxygen-containing atmosphere, cooling, collecting a liquid product, and removing water to obtain small molecular acid; The melting point of the waste high molecular polymer is recorded as T m, and the temperature of the oxidation reaction is not lower than T m -20 ℃ and not higher than T m +50 ℃. The application discloses a catalyst-free low-temperature oxidation method of waste high-molecular polymers, which is characterized in that hydroxyl radicals spontaneously generated by a microdroplet interface are oxidized to obtain small-molecular acids, wherein the microdroplet interface comprises an oxygen-water (gas-liquid) interface and a water-melte