Transition metal-doped Zn-Co spinel catalysts for enhanced aromatic nitriles synthesis via catalytic co-pyrolysis of PET and urea

The co‑catalytic pyrolysis of waste polyethylene terephthalate (PET) with urea under an Ar atmosphere offers a sustainable route to prepare high‑value aromatic nitriles from plastic‑waste recycling. However, low aromatic nitrile yields greatly hinder the scaled-up deployment and practical use of this PET pyrolysis strategy. This work uses transition metal (Ni, Cu, Mn)-doped Zn-Co spinel catalysts to regulate the product distribution during the catalytic pyrolysis of PET-urea mixtures to produce aromatic nitriles. The results reveal that the nickel-doping spinel catalyst exhibits the optimal promotion effect. After adding 10 wt% catalyst with a total mass of PET-urea mixture, the normalized GC-MS peak-area percentages of nitrogen-containing compounds and nitriles in liquid condensate reach 94.6% and 52.3% at 550 ℃, respectively. Compared with the non-catalyst system, the relative contents of nitrogen-containing compounds and nitriles increased by 7.95% and 30.39%, respectively. Among all aromatic nitriles, 1,4-benzenedicarbonitrile shows a relative proportion of 22.7%. Further results indicate that the Ni-doped spinel catalyst facilitates the formation of C N-containing intermediates during the PET-urea co-pyrolysis process. This work presents a catalytic method to raise the relative content of aromatic nitriles in condensed liquid from the argon‑atmosphere PET‑urea catalytic co‑pyrolysis.