The formation of hydrogen in ethylene pyrolysis at 900 K

Ethylene at concentrations of 2.7 × 10^?3 to 1.0 × 10^?2 mol L^?1 has been pyrolyzed at 900 K in a flow system. The products ethane and hydrogen have been analyzed by gas chromatography. The results are consistent with a mechanism in which these products are initially formed as follows: Reaction 1] occurs only 1 to 2% as often as the addition reaction, The latter reaction is close to equilibrium. Taking the rate constant, k₄, and the equilibrium constant, K₂, from the literature and making small adjustments for minor processes, k₁ is found to be (9 ± 3) × 10⁷ L mol^?1 s^?1. Here the uncertainty is intended to encompass errors in the present work and in the literature parameters. A secondary source of hydrogen was also observed. Its dependence on ethylene concentration was consistent with formation from an intermediate with six carbon atoms, such as cyclohexene.