Pyrolysis of Neopentane in a Single Pulse Shock Tube: The Pressure Dependence of the Rate Constant for the C─C Bond Cleavage of Neopentane

ABSTRACT The pyrolysis of neopentane (2,2‐dimethylpropane) has been the subject of investigation at two pressures, approximately 2 and 10 atm, and a range of temperatures from 1000 to 1300 K. A single pulse shock tube was employed to measure the species concentration profiles of the reactant, intermediates, and products by means of gas chromatography (GC) sampling at a reaction time of 1.4 ms. The estimated reaction rate constants for C─C bond cleavage in neopentane (R1), derived from the fitting of a reaction model simulation to the concentration profiles of neopentane, can be represented by the following equations: k R1 = 5.0 × 10 13 exp(−64,100 cal mol −1 / RT ) s −1 and k R1 = 1.0 × 10 14 exp(−63,300 cal mol −1 / RT ) s −1 at 2 and 10 atm, respectively. The rate constants obtained, together with comparisons with literature values, indicate that the rate of C─C bond cleavage of neopentane is in the fall‐off region under the present experimental conditions. It is important to note that the estimated rate constants may be overestimated at low temperatures. This is due to the assumption of a linear relationship between the logarithm of the rate constant and the inverse of the temperature, as is evident from the fitting to the Arrhenius equation A exp(− E a / RT ). A rate‐of‐consumption/production analysis was performed for neopentane and isobutene at 2 and 10 atm to investigate the influence of secondary reactions. Assuming a 50% uncertainty in the hydrogen abstraction reactions by both methyl radicals and hydrogen atoms from the C─H bond, k R1 was estimated to have 38% and 43% uncertainties at 2 and 10 atm, respectively.