Assessment of co-pyrolysis of polyethylene terephthalate with waste cooking oil: Kinetic study and impact on the chemical constituents of the liquid product

Abstract

Post-consumer waste management systems have proven insufficient to meet the growing global demand. In this context, adopting alternative pathways that complement established practices, such as chemical recycling, becomes essential. Accordingly, this study evaluated the potential of the co-pyrolysis process to manage polyethylene terephthalate (PET) residues and waste cooking oil (WCO), converting them into industrial inputs. Three mixing ratios between PET and WCO were evaluated, assessing their synergistic effects through kinetic studies and comprehensive characterization of the final liquid product. The interaction between PET and WCO in the evaluated mixtures reduced the activation energy of thermal degradation by ∼ 40 % compared to raw PET, improving the energy viability of the process. The addition of WCO to the thermal conversion of PET favored the cracking of the polymer, thus the yield of the pyrolytic liquid increased from 44.41 % by weight to 59.38 % in the PW (2:1) mixture, 71.06 % in PW (1:1) and 79.86 % in PW (1:2). The synergistic interaction between the feedstocks led to an increase in terephthalic acid (TPA) production compared to the individual pyrolysis of PET. When PET and WCO were mixed in proportions of 2:1, 1:1, and 1:2, TPA production increased by 167 %, 73 % and 58 %, respectively. Moreover, the production of highly aromatic compounds was inhibited during co-pyrolysis, favoring the formation of less aromatic species. The results showed that the simultaneous management of wastes from co-pyrolysis offers advantages to the production process, presenting itself as a promising approach for the management and production of chemical inputs from PET and WCO.