SCI和EI收录∣中国化工学会会刊

Chinese Journal of Chemical Engineering ›› 2022, Vol. 51 ›› Issue (11): 53-60.DOI: 10.1016/j.cjche.2021.10.028

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Towards recycling purpose: Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Yueqing Wang1, Hongxing Wang2, Hongmei Chen3, Hantao Liu1   

  1. 1. School of Energy and Power Engineering, North University of China, Taiyuan 030051, China;
    2. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China;
    3. School of Instrument and Electronics, North University of China, Taiyuan 030051, China
  • Received:2021-07-13 Revised:2021-10-14 Online:2023-01-18 Published:2022-11-18
  • Contact: Yueqing Wang,E-mail:yueqingwang@nuc.edu.cn;Hantao Liu,E-mail:rcspseet@126.com
  • Supported by:
    This work thanks to the support of the National Natural Science Foundation of China (22005276).

Towards recycling purpose: Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Yueqing Wang1, Hongxing Wang2, Hongmei Chen3, Hantao Liu1   

  1. 1. School of Energy and Power Engineering, North University of China, Taiyuan 030051, China;
    2. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China;
    3. School of Instrument and Electronics, North University of China, Taiyuan 030051, China
  • 通讯作者: Yueqing Wang,E-mail:yueqingwang@nuc.edu.cn;Hantao Liu,E-mail:rcspseet@126.com
  • 基金资助:
    This work thanks to the support of the National Natural Science Foundation of China (22005276).

Abstract: Converting polyethylene terephthalate (PET) wastes to its monomer and valuable chemicals via eco-friendly chemical method is still a challenge task. Previously, phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction. Here, we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling. The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value. Among them, [C16H33N(CH3)3]3PW12O40 (abbreviated as [CTA]3PW) exhibits the highest activity and the most suitable pH responsive values. Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET, but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid. Additionally, the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive [CTA]3PW.

Key words: Polyethylene terephthalate, Alkaline hydrolysis, pH-responsive catalyst, Terephthalic acid

摘要: Converting polyethylene terephthalate (PET) wastes to its monomer and valuable chemicals via eco-friendly chemical method is still a challenge task. Previously, phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction. Here, we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling. The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value. Among them, [C16H33N(CH3)3]3PW12O40 (abbreviated as [CTA]3PW) exhibits the highest activity and the most suitable pH responsive values. Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET, but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid. Additionally, the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive [CTA]3PW.

关键词: Polyethylene terephthalate, Alkaline hydrolysis, pH-responsive catalyst, Terephthalic acid