Carbon nanotubes from post-consumer waste plastics: Investigations into catalyst metal and support material characteristics

Carbon nanotubes were produced from post-consumer mixed waste plastics using a pyrolysis-catalysis process. The catalysts used were Ni-Fe bimetals supported over four different porous materials. The Ni-Fe/MCM41 catalyst displayed the highest catalytic activity for the pyrolysis-catalysis of the waste plastics in terms of carbon material yield at 55.60 wt.%. The order of catalytic activity was Ni-Fe/MCM41> Ni-Fe/ZSM5> Ni-Fe/Beta > Ni-Fe/NKF5, which was closely related to their differences in catalyst pore volume and catalyst reducibility. Formation of Ni-Fe alloy with fine particle dispersion over the Ni-Fe/MCM41 catalyst is suggested to be crucial for the promotion of the decomposition of the carbon precursors and subsequent precipitation to form carbon nanotubes. Whereas, the large catalyst particle size for the Ni-Fe/Beta catalyst led to irregular carbon shapes with a simultaneous decrease in purity and graphitization of the nanotubes. By-product production of hydrogen in large quantities (38.10 mmol H-2 g(plastic)(-1)) could be used as process fuel.

Automated summary

In this study, carbon nanotubes were produced from post-consumer mixed waste plastics using a pyrolysis-catalysis process, with the Ni-Fe/MCM41 catalyst displaying the highest catalytic activity. The order of catalytic activity was related to differences in catalyst pore volume and catalyst reducibility, with the formation of a Ni-Fe alloy suggested to be crucial for the promotion of carbon nanotube formation. By-product production of hydrogen at large quantities could be utilized as process fuel.