Chemical upcycling of PVC-containing plastic wastes by thermal degradation and catalysis in a chlorine-rich environment

Jisong Kang, Ju Young Kim, Suhyeon Sung, Yerin Lee, Sangseo Gu, Jae Wook Choi, Chun Jae Yoo, Dong Jin Suh, Jungkyu Choi, Jeong Myeong Ha

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

Chlorine (Cl)-containing chemicals, including hydrogen chloride, generated during thermal degradation of polyvinyl chloride (PVC) and corresponding mixture impede the chemical recycling of PVC-containing plastic wastes. While upgrading plastic-derived vapors, the presence of Cl-containing chemicals may deactivate the catalysts. Accordingly, herein, catalytic upgrading of pyrolysis vapor prepared from a mixture of PVC and polyolefins is performed using a fixed-bed reactor comprising zeolites. Among the H-forms of zeolites (namely, ZSM-5, Y, β, and chabazite) used in this study, a higher yield of gas products composed of hydrocarbons with lower carbon numbers is obtained using H-ZSM-5, thus indicating further decomposition of the pyrolysis vapor to C1–C4 hydrocarbons on it. Although the formation of aromatic compounds is better on H-ZSM-5, product distributions can be adjusted by further modifying the acidic properties via the alteration of the Si/Al molar ratio, and maximum yields of C1–C4 compounds (60.8%) and olefins (64.7%) are achieved using a Si/Al molar ratio of 50. Additionally, metal ion exchange on H-ZSM-5 is conducted, and upgrading of PVC-containing waste-derived vapor to aromatic chemicals and small hydrocarbon molecules was successfully performed using Co-substituted H-ZSM-5. It reveals that the highest yield of gas products on 1.74 wt% cobalt (Co)-substituted H-ZSM-5 is acquired via the selection of an appropriate metal and metal ion concentration adjustment. Nevertheless, introduction of excess Co into the H-ZSM-5 surface decreases the cracking activity, thereby implying that highly distributed Co is required to achieve excellent cracking activity. The addition of Co also adjusted the acid types of H-ZSM-5, and more Lewis acid sites compared to Brønsted acid sites selectively produced olefins and naphthenes over paraffins and aromatics. The proposed approach can be a feasible process to produce valuable petroleum-replacing chemicals from Cl-containing mixed plastic wastes, contributing to the closed loops for upcycling plastic wastes.

Original languageEnglish
Article number123074
JournalEnvironmental Pollution
Volume342
DOIs
Publication statusPublished - 2024 Feb 1

Bibliographical note

Publisher Copyright:
© 2023 The Authors

Keywords

  • Catalyst
  • Metal ion-exchanged zeolites
  • Plastic pyrolysis
  • PVC

ASJC Scopus subject areas

  • Toxicology
  • Pollution
  • Health, Toxicology and Mutagenesis

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