An experimental and computational study of methyl ester decomposition pathways using shock tubes

Aamir Farooq, D. F. Davidson, R. K. Hanson, L. K. Huynh, A. Violi

Research output: Contribution to journalConference articlepeer-review

85 Scopus citations

Abstract

The high-temperature decomposition of three simple methyl esters: methyl acetate, methyl propionate and methyl butanoate, were studied behind reflected shock waves using tunable diode laser absorption of CO2 near 2.7 μm. CO2 yield measurements were made over the range of temperatures 1260-1653 K, pressures of 1.4-1.7 atm and reactant concentrations of 2-3%, with the balance Ar. The CO2 absorption strengths near 2.7 μm are approximately 50 to 1000 times stronger than the bands near 2.0 and 1.55 μm, respectively, and offer opportunities for significantly more sensitive and accurate combustion measurements than previous absorption work using CO2 bands at shorter wavelength. The experiments provide the first laser-based time-history measurements of the CO2 yields during pyrolysis of these bio-die-sel surrogate fuels in a shock tube. Model predictions for CO2 yields during methyl butanoate pyrolysis at high temperatures, using the detailed reaction mechanisms of [E. M. Fisher, W. J. Pitz, H. J. Curran, C. K. Westbrook, Proc. Combust. Inst. 28 (2000) 1579-1586.] and others, are significantly lower than those measured in this study. However, an improved methyl butanoate model which extends the recent theoretical work of [L.K. Huynh, A. Violi, J. Org. Chem. 73 (2008) 94-101.] provides substantially improved predictions of CO2 yields during methyl butanoate pyrolysis. As earlier mechanisms predicted low yields of CO2 from methyl butanoate decomposition, these new findings imply that existing bio-diesel fuel models, which rely on the rapid formation of two oxygenate radicals from methyl esters (rather than a single non-reactive CO2 molecule) to account for the tendency for soot reduction, may have to be revisited.

Original languageEnglish (US)
Pages (from-to)247-253
Number of pages7
JournalProceedings of the Combustion Institute
Volume32 I
Issue number1
DOIs
StatePublished - Jan 1 2009
Event32nd International Symposium on Combustion - Montreal, QC, Canada
Duration: Aug 3 2008Aug 8 2008

Keywords

  • Laser absorption
  • Methyl butanonate
  • Methyl ester
  • Shock tube

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

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