Mechanistic study on the co-pyrolysis of cellulose and LDPE: Activation energy variations and functional group evolution

The pyrolysis experiments of cellulose (CE), low-density polyethylene (LDPE), and their mixture at a mass ratio of 7:3 were carried out using a thermogravimetric analyzer (TGA). The Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) models were employed to comprehensively analyze the activation energy variations in the reaction system. TG-IR was used to investigate the changes in the functional groups of pyrolysis volatiles, while in-situ infrared spectroscopy was utilized to elucidate the evolution mechanism of functional groups in the solid matrix. The results demonstrated that the co-pyrolysis of CE and LDPE occurs in two distinct stages: predominant cellulose pyrolysis (200–400 °C) and the co-pyrolysis of cellulose char and LDPE (400–500 °C). In the low-temperature stage (∼350 °C), intermediates generated from LDPE pyrolysis facilitated the release of volatiles from CE, resulting in an increase of approximately 10.61 % in the maximum weight loss rate compared to the pyrolysis of CE alone. Additionally, these intermediates also promoted the removal of functional groups from the char formed during CE pyrolysis.