Valorization of waste PET: Understanding the role of active ammonia in facilitating PET depolymerization and aromatic nitrile formation.

Realizing the recovery and valorization of waste polyethylene terephthalate (PET) plastics into value-added products have gained significant importance. This study successfully synthesized aromatic nitriles, specifically terephthalonitrile (TPN), from waste polyethylene terephthalate (PET) plastic through in situ catalytic pyrolysis with urea and γ-Al 2 O 3 catalyst. Based on distributed activation energy model, positive interaction between waste PET and urea is responsible for improved thermal decomposition kinetics. The dosage of urea and pyrolysis temperature significantly influenced TPN production. TPN yield reached 32.5% with ca. selectivity of 85% at 550 °C and equivalent urea dosage. Density functional theory calculations validated the role of active ammonia in reducing energy barriers and thus facilitating PET depolymerization. The study highlights the feasibility of recycling waste PET into valuable aromatic nitriles through in situ catalytic pyrolysis with urea and enhances the understanding of the pyrolysis process. [Display omitted] • Feasibility of recycling waste PET into valuable aromatic nitriles highlighted. • Enhanced thermal decomposition kinetics through positive PET-urea interaction. • 32.5% of terephthalonitrile with 85% selectivity was achieved at optimal conditions. • Influence of urea dosage and pyrolysis temperature on TPN production. • Density functional theory calculations validate role of NH 3 in PET depolymerization. [ABSTRACT FROM AUTHOR]