Flow reactor studies and kinetic modeling of the H-2/O-2 reaction

Profile measurements of the H-2/O-2 reaction have been obtained using a var iable 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 beh avior of the system and place significant emphasis on HO2 and H2O2 kinetics . The explosion limits of dilute H-2/O-2/N-2 mixtures extend to higher pres sures and temperatures than those previously observed for undiluted H2O2 mi xtures. In addition, the explosion limit data exhibit a marked transition t o an extended second limit which runs parallel to the second limit criteria calculated by assuming HO2 formation to be terminating. The experimental d ata and modeling results show that the extended second limit remains an imp ortant boundary in H2/O2 kinetics. Near this limit, small increases in pres sure can result in more than a two order of magnitude reduction in reaction rate. At conditions above the extended second limit, the reaction is chara cterized by an overall activation energy much higher than in the chain expl osive regime. The overall data set, consisting primarily of experimentally measured profi les of H-2, O-2, H2O, and temperature, further expand the data base used fo r comprehensive mechanism development for the H2/O2 and CO/H2O/O-2 systems. Several rate constants recommended in an earlier reaction mechanism have b een modified using recently published rate constant data for H + O-2 (+ N-2 ) = HO2(+ N-2), HO2 + OH = H2O + O-2, and HO2 + HO2 = H2O2 + O-2. When thes e new rate constants are incorporated into the reaction mechanism. model pr edictions are in very good agreement with the experimental data. (C) 1999 J ohn Wiley & Sons, Inc.