Interactions between acetylene and carbon nanotubes at 893 and 1019 K

Abstract

Acetylene was pyrolysed at 893 and 1019 K, at pressures between 31.5 and 109 Torr, and at residence times between 23 and 451 ms. By electron microscopy, carbon nanotubes were observed to be formed on the quartz surface. Carbon formation was monitored by laser extinction at unusually low conversions (0.1–1.5%). Formation of gaseous products was followed by gas chromatography. Boosting the radical concentration in the gas phase by adding acetone increased the rate of formation of carbon. The carbon deposit was found to inhibit the formation of gaseous products by a heterogeneous termination process. HNO 3, HF, LiOH/KOH/H 3BO 3, and Li 3PO 4/K 3PO 4, were used to treat the quartz surface of the reactor. Washing the reactor with HF solution almost eliminated both the formation of nanotubes on the surface and the resulting inhibition of the formation of gaseous products. Acetylene and intermediates formed directly from acetylene were shown to be the main precursors of the formation of carbon nanotubes.