Determination of the rate constant for thermal cracking of methane by means of adiabatic compression and expansion

An improved method was used for reinterpretation of data obtained by Markevich et al. on the thermal cracking of methane in an apparatus for adiabatic compression and expansion (within the range of 1590° to 1750°K at a pressure of ca 20 atm). A rate constant k=1×1015 exp (−103,000/RT) was obtained for the primary reaction step. The latter was suggested to be CH4→CH3+H. It follows from theoretical evaluation of the rate constant for unimolecular methane decomposition by a second-order reaction that, under the experimental conditions used, this process will be first order.