A General Mechanism for the High-Temperature Pyrolysis of Alkanes. The Pyrolysis of Isobutane

A general mechanism is proposed to predict the kinetics of pyrolysis of alkanes at high temperatures (> 1000 K), based on theoretical considerations and on existing literature data. An experimental investigation of the pyrolysis of isobutane in a single-pulse shock tube over the temperature range 1200–1500 K is reported and the results are used to test the proposed mechanism. Computer modelling demonstrates that the mechanism is adequate to explain the experimental data provided that the following are included: ‘forbidden' isomerization reactions, non-Arrhenius rate constants for the methyl radical abstraction reactions, and the addition of hydrogen atoms to olefins. Although further refinement of the mechanism is to be expected as more data becomes available, it already enables pyrolytic behaviour to be predicted for a wide range of alkanes. The investigation also demonstrates how computer modelling can provide insight into a reaction mechanism even when the number of unknowns exceeds the independent experimental data available.