Comparative study on the synergistic co-pyrolysis of plastics and rubber waste: thermal behavior and product distributions

Abstract The huge market demand, large annual yield, wide application, and massive discard of plastics and tires have brought severe environmental issues. It is urgent to find an efficient way to recycle waste plastics and tires as high-value chemicals and energy fuels. Pyrolysis has long been considered a clean and productive technology. However, waste polymers are complex mixtures. The co-pyrolysis of the mixture is difficult but essential for energy and material recovery. This study investigated the co-pyrolysis of PE, PS, PVC, and TW using Thermogravimetric analysis, Pyrolysis-Gas Chromatography/Mass Spectrometry, and lab scale experiments at 550°C. The results revealed significant synergistic effects between different polymers. The interaction effect was reflected by thermal behavior, product distribution, and product components. There were also differences between lab scale programmed heating pyrolysis and micro-scale fast pyrolysis. The interaction of PE/PVC and PE/TW improved olefin yield due to the synergistic effect. While aromatics formation was promoted by PS/TW and PVC/TW. It can be deduced that PE had a positive effect on chain scission reaction, while PS and PVC induced cyclization and aromatization reactions. The possible reaction pathways were proposed to get a better understanding of co-pyrolysis. Our study provided theoretical guidance for mixed polymer co-pyrolysis and product regulation.