Flow reactor studies and kinetic modeling of the H2/O2 reaction

Abstract

Profile measurements of the H2/O2 reaction have been obtained using a variable pressure flow reactor over pressure and temperature ranges of 0.3–15.7 atm and 850–1040 K, respectively. These data span the explosion limit behavior of the system and place significant emphasis on HO2 and H2O2 kinetics. The explosion limits of dilute H2/O2/N2 mixtures extend to higher pressures and temperatures than those previously observed for undiluted H2/O2 mixtures. In addition, the explosion limit data exhibit a marked transition to an extended second limit which runs parallel to the second limit criteria calculated by assuming HO2 formation to be terminating. The experimental data and modeling results show that the extended second limit remains an important boundary in H2/O2 kinetics. Near this limit, small increases in pressure can result in more than a two order of magnitude reduction in reaction rate. At conditions above the extended second limit, the reaction is characterized by an overall activation energy much higher than in the chain explosive regime. The overall data set, consisting primarily of experimentally measured profiles of H2, O2, H2O, and temperature, further expand the data base used for comprehensive mechanism development for the H2/O2 and CO/H2O/O2 systems. Several rate constants recommended in an earlier reaction mechanism have been modified using recently published rate constant data for H + O2 (+ N2) = HO2 (+ N2), HO2 + OH = H2O + O2, and HO2 + HO2 = H2O2 + O2. When these new rate constants are incorporated into the reaction mechanism, model predictions are in very good agreement with the experimental data. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 113–125, 1999