Comprehensive Kinetic Study of PET Pyrolysis Using TGA

Abstract

The pyrolysis of polyethylene terephthalate (PET) is a well-known process for producing high fuel value. This paper aims to study the kinetics of PET pyrolysis reactions at 4 different heating rates (2, 5, 10, and 20 K min^-1) using thermogravimetric analysis (TGA) data. TGA data show only one kinetic reaction within the temperature ranges of 650 to 750 K. Five different model-free models, namely, the Freidman (FR), Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS), Starink (STK), and distributed activation energy model (DAEM), were fitted to the experimental data to obtain the activation energy (<i>E_a</i>) and the pre-exponential factor (<i>A</i>₀) of the reaction kinetics. The Coats-Redfern (CR) model equation was fitted with the help of master plot (Criado's) to identify the most convenient reaction mechanism for this system. <i>E_a</i>'s values were determined by the application of the five aforementioned models and were found to possess an average value of 212 kJ mol^-1. The mechanism of PET pyrolysis reaction was best described by first-order reaction kinetics; this was confirmed by the compensation. Further thermodynamic parameter analysis indicated that the reaction was endothermic in nature.