Study on the effects of aging on the pyrolysis of plastic and the synergistic mechanisms of co-pyrolysis with lignite

Co-pyrolysis of waste plastic with low-rank coal explored how photoaging impacts the pyrolysis of plastics and delves into the synergistic mechanisms involved in co-pyrolysis. The results of elemental analysis, X-ray powder diffraction and Fourier transform infrared spectroscopy showed that photoaging primarily involves oxidizing and breaking the aliphatic chains in polyethylene (PE), as well as generating oxygen-containing functional groups like hydroxyl (-OH), carbonyl (-C=O), and ether (-C-O), thereby reducing the crystallinity of PE. The results of individual plastic pyrolysis showed that photoaging is beneficial to the generation of gas and tar. Pyrolysis tar of PE samples contains significant amounts of alcohols, and olefins and alkynes (O&As). The results of co-pyrolysis indicated that photoaging can enhance the yields of gas and oil from the co-pyrolysis between PE and Naomaohu (NMH) coal. Co-pyrolysis effectively reduced the relative content of O&As in the tar from the pyrolysis of PE samples alone by 8.0%–29.0 %. The synergistic mechanism of co-pyrolysis between aged PE and NMH involved supplying a significant quantity of hydrogen and hydroxyl radicals by NMH, which react with alkyl radicals generated from PE pyrolysis, leading to the production of additional alkanes and alcohols. These findings offered new insights for a deeper understanding of the co-pyrolysis behaviors between waste plastic and lignite.