Wall-less reactor studies. Part 5.—Neopentane pyrolysis

Abstract

The early stages (0.01–1%) of the pyrolysis of neopentane have been studied in a wall-less reactor between 945 and 1016 K in excess argon at 600 Torr (1 Torr = 133.3 N m^–2). The radical chain mechanism deduced from conventional studies is shown to give a good account of the kinetics of formation of methane and ethane; the rate constants for chain initiation neo-C₅H₁₂→ t-C₄H^.₉+ CH^.₃(1), and chain propagation by methyl radicals CH^.₃+ neo-C₅H₁₂→ CH₄+ C₅H^.₁₁(4), are obtained. The values of the latter agree with the results of conventional studies but the former are approximately ten times smaller than previous estimates. The implications of these rate constants for the thermodynamic values of the t-butyl radical are discussed. By using Δ_fH(t-C₄H^.₉) to obtain the activation energy, the Arrhenius equation for the homogeneous gas-phase rate constant k₁ deduced from the mean experimental value at 983 K, log₁₀(k₁/s^–1)=–2.56 ± 0.02, is k₁/s^–1= 1.38 × 10¹⁵ exp (–40051/T).