Pyrolysis kinetic behavior and TG-FTIR-GC–MS analysis of metallised food packaging plastics

Abstract

Metallised food packaging plastics waste (MFPW) is the most complex fraction of plastic waste ever. Pyrolysis treatment is one of the most promising technologies that could be used to convert the plastic fraction of MFPW into energy products and to recover aluminum fraction mixed with char. Within this frame, this research aims to study the volatile products released from pyrolysis of MFPW and their kinetics by using the TG-FTIR/GC–MS system. The experiments were performed on six different types of MFPW (potato chips, chocolate, bakery, coffee, and biscuits) and its mixture. The developed strategy started with analysis of the selected MFPW samples and the proximate analysis showed that the samples were rich with volatile matter content (till 99.5 wt%). In parallel, DMCHA dissolution treatment was used for preliminary experiments to determine the total number and types of plastic layers in MFPW confined to EVA, PET, and LDPE. Afterwards, the TG-FTIR system was used to investigate the thermal and chemical degradation of the MFPW samples up to 900 °C at different heating rates (5-30˚C/min), while the GC/MS system was used to study the volatile products generated from MFPW samples at the maximum decomposition temperatures (467-485˚C). Finally, the model-free methods (Kissinger, Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, and Friedman) were used to develop the kinetic model of pyrolysis of the MFPW samples. The results showed that the main decomposition of the MFPW samples happened in the range 360-500˚C with mass loss of 67–96%, while the kinetic models indicated that the mean activation energies for the mixture sample were estimated at 288.8 kJ/mol (Kissinger), 287.8 KJ/mol (KAS), 314.5 KJ/mol (FWO), and 307.9 KJ/mol (Friedman). Finally, the FTIR spectra and GC–MS results showed that Propene and Furan (7.6%), 2,4-Dimethyl-1-heptene and Isopropylcyclobutane (43.16%), etc. compounds were strongly present in the released volatile products.