Production of carbon nanotubes via catalytic pyrolysis of waste plastics over Ni/Al2O3 catalyst: The influence of plastic types

Thermochemical conversion is a promising technology to convert waste plastics into high-value chemicals from both an economic and environmental point of view. In this work, the production of carbon nanotubes (CNTs) from catalytic pyrolysis of different types waste plastics over Ni/Al2O3 catalyst was investigated in a two-stage fixed bed reactor. Polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were used as raw material. The results show that PS showed a higher solid carbon yield of 32.24 wt%. PE waste plastic led to the lowest liquid yield and the highest gas yield, which were 28.95 wt% and 39.45 wt%, respectively. In terms of obtained CNTs, PE and PP plastics obtained more high-purity, structured and intertwined multi-wall carbon nanotubes, while PS produced more amorphous carbon. PET plastic had high oxygen content, which was not conducive to the growth of CNTs during the pyrolysis process. In summary, PE and PP plastics were suitable as feedstock for the preparation of high-quality CNTs by pyrolysis catalysis. The work provides basic data support for the research of the production of valuable CNTs from waste plastics.