Co-pyrolysis of biomass and polyethylene: Insights into characteristics, kinetic and evolution paths of the reaction process

Abstract

Investigation on the distribution and mechanism of co-pyrolysis products is vital to the directional control and high-value utilization of agriculture solid wastes. Co-pyrolysis, devolatilization, kinetics characteristics, and evolution paths of corn stalk (CS) and low-density-polyethylene (LDPE) were investigated via thermogravimetric experiments. The co-pyrolysis behaviors could be separated into two stages: firstly, the degradation of CS (150- 400 °C); secondly, the degradation of CS (400- 550 °C). The devolatilization index (DI) increased with the addition of LDPE. Furthermore, a combination of devolatilization chemical analysis with product analysis to analyze the intrinsic mechanism during co-pyrolysis. The results indicated that the yield of alkanes and olefin in gas products increased with the addition of LDPE. Additionally, LDPE pyrolysis maybe abstract hydrogen from CS pyrolysis and evolved into hydrogen, methane, and ethylene. Further, the co-pyrolysis kinetic parameters were computed by using model-free isoconversion methods, which showed promotion of CS pyrolysis and the reduced activation energy. All the activation energy were declined, which indicated a "bidirectional positive effect" during co-pyrolysis. The mean activation energy of P-cellulose (P-CE), P-hemicellulose (P-HM), P-lignin (P-LG), and LDPE decreased by 23.49 %, 12.89 %, 15.36 %, and 27.82 %, respectively. This study further proves the hydrogen donor transfer pathway in the co-pyrolysis process of CS and LDPE, providing theoretical support for the resource utilization of agricultural solid waste.

Keywords: Co-pyrolysis; Corn stalk; Kinetic; Low-density polyethylene; Mechanism.