Thermogravimetric kinetic study of catalytic and non-catalytic pyrolysis of PET bottles and micro carbon rod formation

Abstract

This study examined the thermogravimetric pyrolysis behaviour of Polyethylene Terephthalate (PET) bottles using catalysts like ferrocene (F), red mud (RM), a Ni/Cu/Mo multicomponent catalyst on kieselguhr, and ferrocene-red mud mixtures, with or without hydrogen peroxide. Heating rates of 10, 20, and 30 °C/min were used. The Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) models determined activation energies (Ea), which were lower with catalysts compared to pure PET (189 kJ/mol). The lowest Ea (53 kJ/mol) was achieved with hydrogen peroxide, resulting in complete pyrolysis and no char. SEM analysis of the resulting char showed micro carbon rod (MCR) formations. The best catalyst can be chosen based on the needs of the final product. For example, if MCR creation is the goal, ferrocene and red mud may be the best choice; if full pyrolysis is the goal, H₂O₂ may provide the greatest result. The thermodynamic analysis, including ΔH, ΔG, and ΔS, indicated that the enthalpy values for catalyst-containing PETs are lower than those for pure PET. This suggests that the synergistic effect of catalytic pyrolysis likely reduces the energy required to form the activated complex during the thermal decomposition of PET.