Microwave-catalytic co-pyrolysis of Chlorella vulgaris and marine waste plastics with N-doped bimetallic MOFs-derived additive for high-value oil production: Characteristics and mechanistic analysis

Converting algal biomass into high-quality pyrolysis oil by microwave catalytic pyrolysis shows promising potential, where the choice of appropriate additives is crucial. In this paper, nitrogen-doped bimetallic organic framework derived additive (N-Ni-Co@C) was employed to catalyze the co-pyrolysis of Chlorella vulgaris (CV) and marine waste plastics (MW) to produce hydrocarbon-rich, low-oxygen, low-nitrogen pyrolysis oil. The results showed that nitrogen doping increased pore volume and surface area, which enhanced co-pyrolysis characteristics, pyrolysis oil yield, and aromatic selectivity. The maximum average weight loss rate (0.0323 wt%/s), maximum pyrolysis oil yield (14.04 %) and aromatics yields (35.13 %) were obtained under 30 % N-Ni-Co@C. N-Ni-Co@C exhibited significant nitrogen removal efficiency (60.02 %) in pyrolysis oil by facilitating multiple denitrogenation pathways, including amine-N cleavage and cyclization, nitrile-N condensation, and heterocycle-N stabilization. Furthermore, it promoted the conversion of oxygenated compounds to aromatics, achieving a deoxygenation efficiency of 34.52 %, through dehydroxylation, demethoxylation, and aromatization of hydroxyl ketones and methoxy phenols. Notably, after four cycles, the N-Ni-Co@C additive retained 58 % of its initial catalytic activity, demonstrating its potential for application in algal biomass valorization.