Thermal Behavior and Kinetic Study of the Effects of Zinc-Modified Biochar Catalyst on Lignin and Low-Density Polyethylene (LDPE) Co-Pyrolysis

Abstract. The effects of low-density polyethylene (LDPE) and a zinc-modified biochar catalyst on lignin pyrolysis were analyzed by thermogravimetric analysis (TGA). Thermal decomposition analysis disclosed that lignin and LDPE co-pyrolysis was more complicated than pyrolysis of lignin alone, addition of the catalyst caused a decrease in reaction temperature and a slight increase in the conversion rate, and most of the compounds decomposed at 260°C for lignin alone and at about 450°C for the lignin/LDPE blend. The synergistic effect between lignin and LDPE in co-pyrolysis with the catalyst was also analyzed. The kinetic parameters indicated that lignin pyrolysis was a third-order reaction, while lignin/LDPE co-pyrolysis was a second-order reaction. Addition of LDPE to lignin during pyrolysis lowered the activation energy from 49.10 to 30.26 kJ mol -1 . Analysis of the reaction kinetics revealed that the reaction rate improved with addition of the catalyst. Keywords: Biochar catalyst, LDPE, Lignin co-pyrolysis/pyrolysis, Reaction kinetics, Thermal decomposition.