Inhibition of moist carbon monoxide oxidation by trace amounts of hydrocarbons

R. A. Yetter, F. L. Dryer

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Abstract

The moist carbon monoxide oxidation reaction perturbed by small quantities of hydrocarbons is studied to yield information on the reactions of H, O, OH, and HO2 radicals with hydrocarbons (RH) and on general mechanistic inhibition behavior at temperatures near 1000 K. In particular, the inhibiting action of CH4, C2H6, C3H8, C2H4, C3H6, and C2H2 at pressures below the second explosion limit of CO/H2O/O2 mixtures are reported over the temperature range 1026-1140 K at 1 atm. The kinetics of these mixtures are shown to complement mechanistic studies on RH/O2 mixtures for the development and validation of hierarchical hydrocarbon oxidation reaction mechanisms. Considering all the hydrocarbons studied, the general ranking of effectiveness as an inhibitor was found to follow the order: propene>propane >methane>ethane>ethene>acetylene. In fact, acetylene was observed to always promote the oxidation of moist CO, thus emphasizing the importance of O-atom radical attack rather than OH attack on acetylene. Methodologies are also described which permit assessment of elementary reaction rates from inhibition effects. In order to evaluate the potential of these techniques to yield information on rates of H and HO2 attack on hydrocarbons, these methods were applied to constrained moist CO oxidation inhibitions where RH+OH is most important. In the case of the well studied methane reaction and the lesser studied propene reaction, inhibition studies lead to rate constants of 1.6×1012 cm3/mol-s at 1026 K for CH4 and 8×1012 cm3/mol-s at 1020 K for C3H6, respectively. These values are in good agreement with literature data from other more direct techniques. These results show promise of the approach for determining lesser studied elementary reactions at these temperatures, particularly under reaction conditions where HO2 and H reactions dominate the reaction inhibition characteristics.

Original languageEnglish (US)
Pages (from-to)757-767
Number of pages11
JournalSymposium (International) on Combustion
Volume24
Issue number1
DOIs
StatePublished - 1992

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes

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