Microwave-assisted catalytic pyrolysis of polypropylene for aviation fuel production with Fe/Ni catalysts: A comparison with electrical catalytic pyrolysis

To enhance aviation fuel production from plastic waste and understand the impact of microwave heating on pyrolysis, this study investigated the microwave-assisted catalytic pyrolysis of polypropylene (PP) using Fe/Ni-loaded HY zeolite catalysts (HY-zeolite, Fe/HY, Ni/HY, and FeNi/HY). Gas chromatography-mass spectrometry was employed to analyze the composition of the pyrolysis oil, while the gas composition was determined using a mass spectrometer. The catalytic performances of HY-zeolite, Fe/HY, Ni/HY, and FeNi/HY were assessed, with a catalytic-free experiment serving as a reference. Among these catalysts, FeNi/HY showed the best performance, producing pyrolysis oil rich in naphthenes (23.02 area%), paraffins (34.67 area%), and monocyclic aromatics (31.19 area%), which were favorable for aviation fuel production. The effects of pyrolysis temperature (400, 450, 500, 550, and 600 °C) and microwave power (400, 500, 600, 700, and 800 W) were systematically examined, revealing that 500 °C and 500 W provided the best conditions for both maximum oil yield (67.5 wt%) and superior oil quality. Finally, a comparative study of PP pyrolysis using the same catalysts under electrical and microwave-assisted heating was conducted to determine the specific effects of microwave heating. The results showed that the formation of localized hotspots generated high-temperature microenvironments, which facilitated the cleavage of chemical bonds and the formation of free radicals. Moreover, the combined effect of FeNi/HY and microwave heating significantly increased naphthene production, improving the quality of the resulting aviation fuel.