甲醇促进 PET 在温和条件下碱性解聚

Alkaline depolymerization of PET promoted by methanol under mild conditions

摘要

研究利用 KOH 作为解聚剂降解聚对苯二甲酸乙二醇酯(PET)的工艺路线,以甲醇为助溶剂使反应能在温和条件下进行,并优化 PET 化学降解的反应条件。结果表明:该体系可以明显提高降解效率,KOH 与甲醇最佳物质的量比为 1∶9.2,在常压 120 ℃下 PET 的转化率最高达到了 99.6%,固体产物 TPA 收率为 97.2%;在该温度下甲醇可以直接蒸馏回收并重复使用;体系在无水环境中进行,反应产物是水解产物对苯二甲酸(TPA)而非甲醇解产物;反应是氢氧根离子的催化而不是甲氧基催化,PET 化学降解的反应机制符合碱性水解机制。

Abstract

The process of using KOH as a depolymerization agent to degrade polyethylene terephthalate (PET) was studied. Methanol was used as a cosolvent to make the reaction proceed under mild conditions, and the reaction conditions for chemical degradation of PET were optimized. The results show that the system could significantly improve the degradation efficiency. The optimum molar ratio of KOH to methanol is 1∶9.2. The highest conversion rate of PET reaches 99.6% at 120 ℃ under atmospheric pressure, and the yield of solid product TPA is 97.2%. Methanol can be directly distilled and reused at this temperature. The system is carried out in an anhydrous environment, and the reaction product is the hydrolysis product terephthalic acid (TPA) rather than the methanolysis product. The reaction is catalyzed by hydroxide ions rather than methoxy groups. The reaction mechanism of PET chemical degradation conforms to the alkaline hydrolysis mechanism.

关键词

聚对苯二甲酸乙二醇酯 / 碱性解聚 / 助溶剂 / 回收

Key words

polyethylene terephthalate / alkaline deplymerization / cosolvent / recovery

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基金资助

国家自然科学基金项目(22478437)

国家自然科学基金项目(22078365)

山东省自然科学基金项目(ZR2023MB076)