High-efficient microwave plasma discharging initiated conversion of waste plastics into hydrogen and carbon nanotubes

Large-scale manufacture and discard of plastics cause ever serious white pollution. Chemical recycling has been identified as a promising method to convert waste plastics into fuels and chemical products. In this work, a simple and high-efficient method initiated by microwave plasma discharging is proposed to decompose plastics into hydrogen and carbon nanotubes, wherein iron-based catalysts are used as the microwave susceptor and metal tips are utilized to induce plasma discharging. Iron-based catalysts supported on activated carbons calcinated at 400 °C have displayed the best catalytic activity due to the excellent physicochemical properties. Massive H2 rapidly evolves out in the 25 s with a hydrogen efficiency of over 85%. The yield of H2 with plasma discharging by using Fe/AC-400 catalyst is near 300 mmol·g-1Hplastic, which exhibits a 6 times improvement compared to 41 mmol·g-1Hplastic without plasma discharging by using AC catalyst. Little other gases including CH4, CO and CO2 are detected while high-value carbon nanotubes are fabricated. The continuity test over Fe/AC-400 catalyst with microwave plasma discharging presents the distinct ability to generate CNTs continuously. The decomposition for three kinds of plastics has demonstrated the extremely high universal and potential in practical application for real-world plastic wastes.