Formation of polycyclic aromatic hydrocarbons coincident with pyrolytic carbon deposition

Ethane was pyrolysed in a flow reactor system at residence times from 0.5 t o 20 s, at 1185 K and a pressure of 40 kPa. Liquid products were trapped an d analyzed by liquid chromatography, gas chromatography and mass spectromet ry using atmospheric pressure chemical ionization and electron impact ioniz ation. At least 90 products (with m/z ratios up to 700) were present: of th ese products 19 were identified, and eight were quantified. Benzene was the major liquid product, with a maximum yield of 16% by weight of the feed ga s. Products with even numbers of carbon atoms were prominent, which is cons istent with theories proposing that PAHs grow by the addition of acetylene. Most of the aromatics quantified had maximum yields at about 6 s, coincidi ng with the maximum rate of carbon deposition in the reactor, as recorded b y a micro-balance. This observation is consistent with theories proposing t hat pyrolytic carbon is formed from aromatics. (C) 2001 Elsevier Science Lt d. All rights reserved.