TY - JOUR
T1 - Measurements of H2O2 in low temperature dimethyl ether oxidation
AU - Guo, Huijun
AU - Sun, Wenting
AU - Haas, Francis M.
AU - Farouk, Tanvir
AU - Dryer, Frederick L.
AU - Ju, Yiguang
N1 - Funding Information:
This work was supported by a MURI research grant from the Air Force Office of Scientific Research and the Grant No. FA9550-07-1-0136 and the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center on Combustion with Grant No. DE-SC0001198 . YJ would like to thank Prof. Fei Qi at USTC for many helpful discussions in designing the MBMS system and sending Mr. Huijun Guo to Princeton University as a visiting graduate student for one year.
PY - 2013
Y1 - 2013
N2 - H2O2 is one of the most important species in dimethyl ether (DME) oxidation, acting not only as a marker for low temperature kinetic activity but also responsible for the "hot ignition" transition. This study reports, for the first time, direct measurements of H2O 2 and CH3OCHO, among other intermediate species concentrations in helium-diluted DME oxidation in an atmospheric pressure flow reactor from 490 to 750 K, using molecular beam electron-ionization mass spectrometry (MBMS). H2O2 measurements were directly calibrated, while a number of other species were quantified by both MBMS and micro gas chromatography to achieve cross-validation of the measurements. Experimental results were compared to two different DME kinetic models with an updated rate coefficient for the H + DME reaction, under both zero-dimensional and two-dimensional physical model assumptions. The results confirm that low and intermediate temperature DME oxidation produces significant amounts of H 2O2. Peroxide, as well as O2, DME, CO, and CH3OCHO profiles are reasonably well predicted, though profile predictions for H2/CO2 and CH2O are poor above and below ∼625 K, respectively. The effect of the collisional efficiencies for the H+O2+M=HO2 + M reaction on DME oxidation was investigated by replacing 20% He with 20% CO2. Observed changes in measured H2O2 concentrations agree well with model predictions. The new experimental characterizations of important intermediate species including H2O2, CH2O and CH 3OCHO, and a path flux analysis of the oxidation pathways of DME support that kinetic parameters for decomposition reactions of HOCH 2OCO and HCOOH directly to CO2 may be responsible for model under-prediction of CO2. The H abstraction reactions for DME and/or CH2O and the unimolecular decomposition of HOCH2O merit further scrutiny towards improving the prediction of H2 formation.
AB - H2O2 is one of the most important species in dimethyl ether (DME) oxidation, acting not only as a marker for low temperature kinetic activity but also responsible for the "hot ignition" transition. This study reports, for the first time, direct measurements of H2O 2 and CH3OCHO, among other intermediate species concentrations in helium-diluted DME oxidation in an atmospheric pressure flow reactor from 490 to 750 K, using molecular beam electron-ionization mass spectrometry (MBMS). H2O2 measurements were directly calibrated, while a number of other species were quantified by both MBMS and micro gas chromatography to achieve cross-validation of the measurements. Experimental results were compared to two different DME kinetic models with an updated rate coefficient for the H + DME reaction, under both zero-dimensional and two-dimensional physical model assumptions. The results confirm that low and intermediate temperature DME oxidation produces significant amounts of H 2O2. Peroxide, as well as O2, DME, CO, and CH3OCHO profiles are reasonably well predicted, though profile predictions for H2/CO2 and CH2O are poor above and below ∼625 K, respectively. The effect of the collisional efficiencies for the H+O2+M=HO2 + M reaction on DME oxidation was investigated by replacing 20% He with 20% CO2. Observed changes in measured H2O2 concentrations agree well with model predictions. The new experimental characterizations of important intermediate species including H2O2, CH2O and CH 3OCHO, and a path flux analysis of the oxidation pathways of DME support that kinetic parameters for decomposition reactions of HOCH 2OCO and HCOOH directly to CO2 may be responsible for model under-prediction of CO2. The H abstraction reactions for DME and/or CH2O and the unimolecular decomposition of HOCH2O merit further scrutiny towards improving the prediction of H2 formation.
KW - Dimethyl ether
KW - Flow reactor
KW - Hydrogen peroxide
KW - Low temperature chemistry
KW - Molecular Beam Mass Spectrometry
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U2 - 10.1016/j.proci.2012.05.056
DO - 10.1016/j.proci.2012.05.056
M3 - Article
AN - SCOPUS:84873345962
SN - 1540-7489
VL - 34
SP - 573
EP - 581
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
ER -