Formation of pyrolytic carbon during the pyrolysis of ethane at high conversions

This study reports the amounts of gaseous products and pyrolytic carbon for med during the pyrolysis of ethane under industrially significant condition s. Analytical techniques included gas chromatography, mass spectrometry, an d gravimetric analysis. Changes in the product composition were measured in a how system as a function of residence rime (0.3 to 21 s), pressure (6.7 to 53 kPa) and temperature (1185 to 1100 K). When the initial ethane concen tration was varied, the rate of carbon deposition was found to be proportio nal to the local benzene concentration. The rate of benzene formation was p roportional to the concentration of acetylene cubed. The rate of carbon dep osition, at 40 kPa, reached a maximum after ethane had reacted for similar to6 s, when the concentration of benzene produced was also at a maximum. Th e changes in product composition with residence time were consistent with b enzene, or an intermediate which has a concentration proportional to benzen e, reacting in a rate limiting step on the complex pathway to pyrolytic car bon formation. (C) 2000 Elsevier Science Ltd. All rights reserved.