Continuous flow pyrolysis of virgin and waste polyolefins: a comparative study, process optimization and product characterization

Abstract

Under optimal process conditions, pyrolysis of polyolefins can yield ca. 90 wt % of liquid product, i.e., combination of light oil fraction and heavier wax. In this work, the experimental findings reported in a selected group of publications concerning the non-catalytic pyrolysis of polyolefins were collected, reviewed, and compared with the ones obtained in a continuously operated bench-scale pyrolysis reactor. Optimized process parameters were used for the pyrolysis of waste and virgin counterparts of high-density polyethylene, low-density polyethylene, polypropylene and a defined mixture of those (i.e., 25:25:50 wt %, respectively). To mitigate temperature drops and enhance heat transfer, an increased feed intake is employed to create a hot melt plastic pool. With 1.5 g·min^–1 feed intake, 1.1 L·min^–1 nitrogen flow rate, and a moderate pyrolysis temperature of 450 °C, the formation of light hydrocarbons was favored, while wax formation was limited for polypropylene-rich mixtures. Pyrolysis of virgin plastics yielded more liquid (maximum 73.3 wt %) than that of waste plastics (maximum 66 wt %). Blending polyethylenes with polypropylene favored the production of liquids and increased the formation of gasoline-range hydrocarbons. Gas products were mainly composed of C₃ hydrocarbons, and no hydrogen production was detected due to moderate pyrolysis temperature.

Graphical abstract

Keywords

waste plastics / polyolefins / chemical recycling / pyrolysis / alternative fuels / waste-to-energy

References

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Acknowledgements

The work was supported by an Institutional Links (Grant No. 527641843) under the Türkiye partnership. The grant is funded by the UK Department for Business, Energy and Industrial Strategy together with the Scientific and Technological Research Council of Türkiye (TÜBİTAK; Project No. 119N302) and delivered by the British Council. A grant to Ecrin Ekici by the European Commission for the Erasmus + Internship Mobility Program is gratefully acknowledged. The authors acknowledge support from the KIT-Publication Fund of the Karlsruhe Institute of Technology.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at http://doi.org/10.1007/s11705-024-2429-x and is accessible for authorized users.

Competing interests

The authors declare that they have no competing interests.

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