Insights into the char-production mechanism during co-pyrolysis of biomass and plastic wastes

Co-pyrolysis is a promising method for converting biomass/plastic wastes into high-value-added carbon materials. The mechanism involved in co-pyrolysis process for char production is complex and the relevant information is limited, making it essential to investigate the evolution mechanism. In response, different co-pyrolysis methods (blending with multiple interaction, volatile-volatile interaction, volatile-char interaction) were adopted for bamboo and polyethylene (PE). The char-production mechanism was investigated based on physicochemical properties and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis of char. The addition of PE significantly affected the char properties compared to bamboo pyrolysis. The yield of char increased from 24.80 % to 26.59 % and the specific surface area decreased from 103.64 m2 g−1 to 1.84 m2 g−1. The High H/C ratio, low O/C ratio, low porosity, and high oxidation reactivity of co-pyrolysis char is attribute to hydrodeoxygenation reactions on char surface and the deposition of amorphous carbon on the bamboo char. Experiments with different co-pyrolysis methods revealed a significant synergistic effect between bamboo char and volatiles from PE, with the latter depositing on the former's surface as amorphous carbon. The interaction between bamboo char and volatiles from PE during co-pyrolysis was revealed by in-situ DRIFT analysis, further elucidating the evolution mechanism. A series of hydrodeoxygenation reactions and radical transfer reactions were induced to occur. It is of great significance to further study the mechanism of co-pyrolysis of biomass/plastic wastes.