Chemical recycling of polyolefin waste: from the perspective of efficient pyrolysis reactors

Abstract

Polyolefins, widely used for packaging, construction, and electronics, facilitate daily life but cause severe environmental pollution when discarded after usage. Chemical recycling of polyolefins has received widespread attention for eliminating polyolefin pollution, as it is promising to convert polyolefin wastes to high-value chemicals (e.g., fuels, light olefins, aromatic hydrocarbons). However, the chemical recycling of polyolefins typically involves high-viscosity, high-temperature and high-pressure, and its efficiency depends on the catalytic materials, reaction conditions, and more essentially, on the reactors which are overlooked in previous studies. Herein, this review first introduces the mechanisms and influencing factors of polyolefin waste upcycling, followed by a brief overview of in situ and ex situ processes. Emphatically, the review focuses on the various reactors used in polyolefin recycling (i.e., batch/semi-batch reactor, fixed bed reactor, fluidized bed reactor, conical spouted bed reactor, screw reactor, molten metal bed reactor, vertical falling film reactor, rotary kiln reactor and microwave-assisted reactor) and their respective merits and demerits. Nevertheless, challenges remain in developing highly efficient reacting techniques to realize the practical application. In light of this, the review is concluded with recommendations and prospects to enlighten the future of polyolefin upcycling.

Graphical abstract

Keywords

polyolefins / chemical recycling / thermal pyrolysis / catalytic pyrolysis / reactors

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Competing interests

The authours declare that they have no competing interests.

Acknowledgements

The authors are thankful for the financial support of the National Natural Science Foundation (Grant Nos. 22293061, 22208292); Zhejiang Provincial Natural Science Foundation (Grant Nos. LD24E030003); the State Key Laboratory of Chemical Engineering (Grant Nos. SKL-ChE-23D02, SKL-ChE-23T04); the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering (Grant No 2022SZ-TD003); the Research Funds of Institute of Zhejiang University-Quzhou (Grant Nos. IZQ2021RCZX002, IZQ2021RCZX003, IZQ2021KJ2011 and IZQ2022RCZX201). We also acknowledge the staff from the Analysis & Testing Center, Institute of Zhejiang University-Quzhou, and the State Key Laboratory of Chemical Engineering, Zhejiang University.

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