Thermal hydrogenation of ethylene

Abstract

Detailed product analyses have been used to re-examine the kinetics of the thermal hydrogenation of ethylene at 823.2° K. The reaction forms the same products as the pyrolysis of ethylene and like that reaction is subject to self-acceleration. The results are explained in terms of an extension of the degenerately branched chain mechanism for ethylene pyrolysis; the presence of hydrogen introduces a heterogeneous primary chain initiation. At 823.2° K the reaction C₂H_5*+ H₂→C₂H₆+ H* is (11±3) times more rapid than C₂H_5*+ C₂H₄→C₂H₆+ C₂H_3˙. Velocity constants are derived for these processes and for the degenerate branching reaction C₄H₈→CH_3˙+ C₃H_5˙.