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Frontiers of Chemical Science and Engineering >> 2024, Volume 18, Issue 6 doi: 10.1007/s11705-024-2429-x

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

1. Karlsruhe Institute of Technology, Institute of Catalysis Research and Technology, Eggenstein-Leopoldshafen 76344, Germany;2. Izmir Institute of Technology, Faculty of Engineering, Department of Energy Systems Engineering, Izmir 35430, Türkiye;2. Izmir Institute of Technology, Faculty of Engineering, Department of Energy Systems Engineering, Izmir 35430, Türkiye;3. Department of Materials Engineering and Production, Faculty of Mechanical Engineering, Bialystok University of Technology, Bialystok 15-351, Poland;4. Department of Agricultural and Food Engineering and Environmental Development, Institute of Civil Engineering and Energetics, Faculty of Civil Engineering and Environmental Sciences, Bialystok University of Technology, 15-351 Bialystok, Poland;5. Department of Chemistry, Biology and Biotechnology, Institute of Civil Engineering and Energetics, Faculty of Civil Engineering and Environmental Sciences, Bialystok University of Technology, Bialystok 15-351, Poland;6. Izmir Institute of Technology, Faculty of Engineering, Department of Chemical Engineering, Izmir 35430, Türkiye;7. Energy and Bioproducts Research Institute (EBRI), Aston University, Birmingham B4 7ET, United Kingdom

Received: 2023-11-20 Available online: 2023-11-20

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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.

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