Microwave-assisted pyrolysis of plastic waste with magnetic catalysts in a multi-ridge field compressed reactor

Environmental crises caused by plastic pollution have spurred the development of novel recovery and upcycling methods. In this study, a microwave magnetic field and magnetic catalyst cracking strategy based on a microwave multi-ridge field compressed reactor was proposed to efficiently convert polyethylene into hydrogen and high-quality carbon nanotubes while minimising energy consumption. A series of catalysts with different iron and cobalt contents was prepared and evaluated for hydrogen production from polyethylene cracking. A high hydrogen yield of 61.6 mmol·g−1plastic was obtained in the magnetic field position with an energy consumption of only 5 W·h g−1plastic, whereas the hydrogen yield was 45.7 mmol·g−1plastic under microwave electric field. Under microwave magnetic field activation, the magnetic catalyst CoFeOx exhibited higher selectivity for H2 than hydrocarbons in waste plastics. In addition, high hydrogen yields were achieved by varying the ratio of the catalyst feedstock in the electric field and intermediate positions of the reactor. This reactor separates the microwave fields in the reactor and places catalysts with different absorption characteristics at different positions, which can significantly improve the efficiency of microwave energy utilisation. [Display omitted] •Microwave magnetic field assisted pyrolysis of plastics with magnetic catalysts.•Magnetic catalyst CoFeOx was prepared by citric acid combustion method.•Hydrogen production from polyethylene up to 61.6 mmol·g−1plastic.•Effect of magnetic catalysts on plastic cracking in microwave fields was studied.