Pyrolysis-catalysis of waste plastic using a nickel-stainless steel mesh catalyst for high value carbon products.

A stainless steel mesh loaded with nickel catalyst was produced and used for the pyrolysis-catalysis of waste high density polyethylene with the aim of producing high value carbon products, including carbon nanotubes. The catalysis temperature and plastic to catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel-stainless steel mesh catalyst. Increasing temperature from 700 to 900 °C resulted in an increase in the carbon deposited on the nickel loaded stainless steel mesh catalyst from 32.5 wt.% to 38.0 wt.%. The increase of sample to catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g(-1) plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes. The optimum process conditions for carbon nanotube production, in terms of yield and graphitic nature, determined by Raman spectroscopy, was catalysis temperature of 800 °C and plastic to catalyst ratio of 1:2 where a mass of 334 mg of filamentous/multi-walled carbon nanotubes g(-1) plastic was produced.