Study on high-value products of waste plastics from microwave catalytic pyrolysis: Construction and performance evaluation of advanced microwave absorption-catalytic bifunctional catalysts

A series of bifunctional catalysts (Fe-Ni/SiC) with microwave absorption and catalytic abilities were constructed to realize high-value application of waste plastics by microwave catalytic pyrolysis. The bifunctional performances and mechanisms were explored by a new microwave thermogravimetric oven. The bifunctional catalysts had good pore structure and the active components of Fe2O3, NiO, and NiFe2O4, which made the catalysts with good dielectric and catalytic performances. After catalysis, the heating rates and weight loss rates of low-density polyethylene were 68.18–73.39 °C·min−1 and 0.59–0.68 g·min−1, respectively. The increase in heating rate helped to promote the pyrolysis degree, advance the pyrolysis endpoint, and reduce the energy consumption (11.54 MJ/kg at most). When the catalyst was Fe-Ni/SiC (2:1), the highest gas yield (73.61 wt%) and H2 content (73.89 vol%) was obtained. Moreover, the higher graphitization degree of carbon nanotubes was obtained with more Fe loading. The oriented production of high-value products could be realized by adjusting the type and proportion of active components in the catalyst.