Kinetics of the Nitrous Oxide–Hydrogen Reaction

The reaction of hydrogen with nitrous oxide was studied behind incident shock waves over the temperature range 1700°–2600°K. Experimentally, the concentration profiles of OH and the concentration of NO after the decomposition of N2O were measured by uv absorption. The OH profiles have qualitatively similar features to those determined in the H2–O2 reaction. The concentration of NO after the disappearance of N2O remains constant for several hundred microseconds. Interpretation of the experiments was based on a mechanism which contains the currently accepted data on the H2–O2 reaction and four additional reactions. Computer calculations show that the rate constants for the reaction O+N2O→ lim k32NO as cited in the current literature are too low. The magnitude of k3 determined in this work is consistent with published data on the reverse reaction, and k3 = 6.3 × 1014exp(− 26 700 / RT) cm3mole−1·sec−1 is believed to be correct to within a factor of 3 between 1700° and 4000°K. The present investigation also permitted estimation of the constant for the reaction H+N2O→ lim k5OH+N2. If the literature rate constants for the H2–O2 system are assumed to be correct the best fit to our data is achieved with k5 = 4.0 × 1013exp(− 12 000 / RT). However, a number of inconsistencies remain in the lower temperature range which cannot be reconciled within the framework of the assumed mechanism. These are similar to difficulties which were reported by others on the H2–O2 reaction.