Self-inhibition and mechanism of isobutane pyrolysis

Abstract

The initial stages of the pyrolysis of isobutane have been studied at temperatures between 420 and 570°C. Initial reactant pressures were restricted to the range 300–550 mm Hg in which wall termination of reaction chains is negligible. Particular attention was paid to the self-inhibition of the reaction and to hitherto unreported changes in the distribution of the major products, both of which occur at an unusually early stage in this system. A qualitative account of both phenomena results from the introduction of the reactions, H˙+(CH₃)₂C : CH₂→(CH₃)₃Ċ(–5), and (CH₃)₃Ċ+ C₄H₁₀→(CH₃)₂CHĊH₂+ C₄H₁₀, (7), into the normal Rice-Herzfeld scheme for the propagation of reaction chains. The kinetics of the formation of the major products are compatible with the choice of the mutual reactions of (CH₃)₃Ċ as the sole homogeneous termination processes.