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

This study reports the amounts of gaseous products and pyrolytic carbon formed during the pyrolysis of ethane under industrially significant conditions. Analytical techniques included gas chromatography, mass spectrometry, and 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 concentration was varied, the rate of carbon deposition was found to be proportional to the local benzene concentration. The rate of benzene formation was proportional to the concentration of acetylene cubed. The rate of carbon deposition, 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. The changes in product composition with residence time were consistent with benzene, or an intermediate which has a concentration proportional to benzene, reacting in a rate limiting step on the complex pathway to pyrolytic carbon formation. (C) 2000 Elsevier Science Ltd. All rights reserved.