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. (C) 2010 Elsevier Ltd. All rights reserved.