Thermal decomposition of CH{sub 3}CHO studied by matrix infrared spectroscopy and photoionization mass spectroscopy

Journal Article · Sun Oct 28 00:00:00 EDT 2012 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4759050· OSTI ID:22099066

Vasiliou, AnGayle K. ^[1]; Piech, Krzysztof M.; Reed, Beth; Ellison, G. Barney ^[1]; Xu, Zhang ^[2]; Nimlos, Mark R. ^[3]; Ahmed, Musahid; Golan, Amir; Kostko, Oleg ^[4]; Osborn, David L. ^[5]; David, Donald E. ^[6]; Urness, Kimberly N.; Daily, John W. ^[7]; Stanton, John F. ^[8]

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1. Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215 (United States)
2. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States)
3. National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, Colorado 80401 (United States)
4. Chemical Sciences Division, LBNL MS 6R-2100, Berkeley, California 94720 (United States)
5. Combustion Research Facility, Sandia National Laboratories, P.O. Box 969 MS 9055, Livermore, California 94551-0969 (United States)
6. Integrated Instrument Design Facility, CIRES, University of Colorado, Boulder, Colorado 80309-0216 (United States)
7. Center for Combustion and Environmental Research, Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309-0427 (United States)
8. Institute for Theoretical Chemistry, Department of Chemistry, University of Texas, Austin, Texas 78712 (United States)

A heated SiC microtubular reactor has been used to decompose acetaldehyde and its isotopomers (CH{sub 3}CDO, CD{sub 3}CHO, and CD{sub 3}CDO). The pyrolysis experiments are carried out by passing a dilute mixture of acetaldehyde (roughly 0.1%-1%) entrained in a stream of a buffer gas (either He or Ar) through a heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 50-200 Torr with the SiC tube wall temperature in the range 1200-1900 K. Characteristic residence times in the reactor are 50-200 {mu}s after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 {mu}Torr. The reactor has been modified so that both pulsed and continuous modes can be studied, and results from both flow regimes are presented. Using various detection methods (Fourier transform infrared spectroscopy and both fixed wavelength and tunable synchrotron radiation photoionization mass spectrometry), a number of products formed at early pyrolysis times (roughly 100-200 {mu}s) are identified: H, H{sub 2}, CH{sub 3}, CO, CH{sub 2}=CHOH, HC{identical_to}CH, H{sub 2}O, and CH{sub 2}=C=O; trace quantities of other species are also observed in some of the experiments. Pyrolysis of rare isotopomers of acetaldehyde produces characteristic isotopic signatures in the reaction products, which offers insight into reaction mechanisms that occur in the reactor. In particular, while the principal unimolecular processes appear to be radical decomposition CH{sub 3}CHO (+M) {yields} CH{sub 3}+ H + CO and isomerization of acetaldehyde to vinyl alcohol, it appears that the CH{sub 2}CO and HCCH are formed (perhaps exclusively) by bimolecular reactions, especially those involving hydrogen atom attacks.

• OSTI ID: 22099066
• Journal Information: Journal of Chemical Physics, Vol. 137, Issue 16; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
ACETALDEHYDE
CARBON MONOXIDE
FOURIER TRANSFORM SPECTROMETERS
FOURIER TRANSFORMATION
INFRARED SPECTRA
ISOMERIZATION
MASS SPECTROSCOPY
MOLECULAR BEAMS
PHOTOIONIZATION
PYROLYSIS
REACTION KINETICS
SILICON CARBIDES
SYNCHROTRON RADIATION