Catalytic reforming of polyethylene pyrolysis vapors to naphtha range hydrocarbons with low aromatic content over a high silica ZSM-5 zeolite

Leilei Dai, Nan Zhou, Yuancai Lv, Kirk Cobb, Paul Chen, Yunpu Wang, Yuhuan Liu, Rongge Zou, Hanwu Lei, Badr A. Mohamed, Roger Ruan, Yanling Cheng

Research output: Contribution to journalArticlepeer-review

Abstract

In this study, the microwave-assisted pyrolysis coupled with ex-situ catalytic reforming of polyethylene for naphtha range hydrocarbons, with low aromatic content, was investigated. Experimental results revealed that ZSM-5 zeolites with low SiO2/Al2O3 ratios led to high aromatic selectivity, while an extremely high SiO2/Al2O3 ratio significantly reduced the aromatic selectivity. The high selectivity of C5-C12 hydrocarbons (98.9 %) with low selectivity of C5-C12 aromatics (28.5 %) was obtained over a high silica ZSM-5 zeolite at a pyrolysis temperature of 500 °C, catalytic cracking temperature of 460 °C, and a weight hourly space velocity of 7 h−1. The liquid oil produced was mainly composed of C5-C12 olefins that can be easily converted into paraffin-rich naphtha by hydrogenation or hydrogen transfer reactions as the feedstock for new plastic manufacturing. 8 cycles of regeneration-reaction cycles were carried out successfully with little change on the product distribution, showing the great potential for continuous production of low-aromatic liquid oil. Catalyst characterization showed that the catalyst deactivation was primarily caused by coke deposition (approximately 16.0 wt%) on the surface of the catalysts, and oxidative regeneration was able to recover most of the pore structure and acidity of the zeolite by effectively removing coke. This study provides a better understanding for the plastic-to-naphtha process and even for scale-up studies.

Original languageEnglish (US)
Article number157658
JournalScience of the Total Environment
Volume847
DOIs
StatePublished - Nov 15 2022

Bibliographical note

Funding Information:
We acknowledge the financial support from the National Natural Science Foundation of China ( 21766019 , 21878137 ), The Centrally Guided Local Science Technology Special Project ( 20202ZDB01012 ), the Major Discipline Academic and Technical Leaders Training Program of Jiangxi Province ( 20204BCJ23011 ), China Scholarship Council (CSC), Xcel Energy , Resynergi , the University of Minnesota MnDrive Environment Program MNE12, and the University of Minnesota Center for Biorefining. Parts of this work were carried out in the Characterization Facility, University of Minnesota , which receives partial support from NSF through the MRSEC program.

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • Low aromatic naphtha
  • Microwave-assisted pyrolysis
  • Waste plastic
  • Zeolite catalysis

PubMed: MeSH publication types

  • Journal Article

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