Study on pyrolysis characteristics and kinetics of mixed waste plastics under different atmospheres

The Thermochemical method (pyrolysis) is the most promising means to treat waste plastics, which can be converted into high value-added products with significant economic and social benefits. In this study, the py-rolysis characteristics of single/mixed plastics under different atmospheres (nitrogen, carbon dioxide) were explored, and two kinetic models (KAS method and Friedman method) were used to calculate the kinetic pa-rameters. The experimental results showed that carbon dioxide (CO2) atmosphere can reduce the pyrolysis temperature of plastics. At the same time, the activation energy of single plastics under carbon dioxide (CO2) atmosphere was lower than that of nitrogen atmosphere (N2), with a decrease of about 7-60 kJ/mol, and the activation energy calculation results of mixed plastics were roughly similar. There was a positive synergistic effect between the mixed plastics under N2 atmosphere, and the activation energy decreased from 234 kJ/mol to 221 kJ/mol, with a decrease of about 6%. There was a negative synergistic effect between the mixed plastics under CO2 atmosphere, and the activation energy increased from 206 kJ/mol to 219 kJ/mol, with an increase of about 6%. The theoretical TG curve method also obtained similar conclusions. This experimental investigation can provide theoretical support for the environmentally friendly recycling technology of plastic waste.