Co-pyrolysis characteristics and pyrolysis oil analysis of Chlorella vulgaris and marine waste plastics with multi-metal MOFs-derived additive

Abstract

In this study, MOFs-derived additives with microwave absorption and catalytic characteristics were employed in the microwave co-pyrolysis of Chlorella vulgaris (CV) and marine waste plastics (MW) to produce high-quality pyrolysis oil. The effects of additives (Ni-Cu@C, Ni-Co@C, Cu-Co@C and Ni-Cu-Co@C) under different addition amounts (10%, 20%, 30%) on co-pyrolysis characteristics, product yield and pyrolysis oil composition were investigated. Furthermore, the pyrolysis mechanism was analyzed. The results showed that the MOFs-derived additives improved the co-pyrolysis characteristics, especially at 30% addition amount. The maximum average weight loss rate (0.0273 wt.%/s) and pyrolysis oil yield (14.33%) obtained at 30% Ni-Cu-Co@C group. Moreover, the aromatic content (30.07%), deoxygenation efficiency (27.70%) and denitrogenation efficiency (80.03%) in pyrolysis oil were maximum at adding 30% Ni-Cu-Co@C. Ni-Cu-Co@C promoted the nitrogen transformation into gaseous products, while reduced the nitrogen contents in char and pyrolysis oil. Meanwhile, the nitrogen in char was dominated by pyridine-N and quaternary-N. Importantly, the activity of the Ni-Cu-Co@C remained 0.66 times of the initial activity after 5 cycles, demonstrating the excellent regenerative usability.