Deep insights on the Co-pyrolysis of tea stem and polyethylene terephthalate (PET): Unveiling synergistic effects and detailed kinetic modeling

Abstract

This study investigates the co-pyrolysis of tea stem (TS) and polyethylene terephthalate (PET), with an emphasis on their interactions during the pyrolysis process. The effects of heating rate and TS/PET ratio on synergy of TS with PET pyrolysis was examined using thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) techniques. The experimental runs were conducted at three mixing ratios (i.e., 3:1, 1:1, and 1:3) of TS to PET and four heating rates (i.e., 10, 15, 20, and 25 °C/min). The results show that the TS/PET ratio is the main factor determining the synergy of the two components. In particular, the mixture of 25 % TS and 75 % PET exhibited the least antagonistic effects, while the mixture of 75 % TS and 25 % PET had strong synergistic positive and negative effects. Moreover, the FT-IR analysis of the co-pyrolysis process suggested the presence of oxygenated compounds, including hydroxyl and carbonyl groups, indicating the potential formation of aromatic hydrocarbons in the co-pyrolysis process. A new kinetic modeling approach including seven independent parallel reactions (IPR), was developed to illustrate the complex decomposition behavior of the TS-PET mixture. The outcome of kinetic modeling using nonlinear multivariate optimization resulted in a quality of fit ranging from 1.38 % to 3.55 %. These results accurately depict the experimental evidence and offer useful understanding of the reaction kinetics and the overall influence of the mixing ratio on the kinetic triplets.