Synthesis of carbon nanotubes by sequential pyrolysis and combustion of polyethylene

Carbon nanotubes (CNTs) were synthesized from polyethylene using a pyrolysis–combustion technique. Pre- or post-consumer polyethylene (in strips, pellets or ground particles) was pyrolyzed to gaseous products, which were then combined with an oxygen-containing gas and auto-ignited to create a fuel-rich flame. The combustion effluent was used to synthesize multi-wall CNTs using stainless-steel wire mesh as both catalyst and substrate. An overall CNT yield in the order of 10%, by mass relative to the initial carbon in the fuel, was typically achieved before purification. The viability of partial conversion of a readily-available waste stream to the value-added product of CNTs was demonstrated, combining the economy and process safety aspects of flame synthesis with the control of synthesis temperature that chemical vapor deposition methods typically afford.