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Molecular -beam mass spectrometry and modeling of a propylene /chlorine reactive flow and an ethylene flame doped with allene

George Edward Oulundsen, University of Massachusetts Amherst


Axial mole-fraction profiles were measured in a low-pressure reactive flow of propylene/chlorine and a low-pressure, fuel-rich ethylene flame doped with allene. The purpose was to generate data and test models for improving allyl chloride production and pollutant-related C3 flame chemistry. Molecular-beam mass spectrometry was the principal analytical technique. The propylene/chlorine system had feed conditions of 71.2% propylene and 28.8% chlorine, 76.00 ± 0.01 Torr, and 17.5 cm/s burner-surface gas velocity (298 K). Because propylene and chlorine could pre-react, a novel multidiffusion burner was developed. Mole fraction profiles were mapped for seven stable species. Temperature measurements were made using a K-type thermocouple, and the constant flow cross-section was determined visually. By modeling as a plug-flow reactor with literature rate constants and data and rate constants determined here, a self-consistent reaction mechanism was constructed and used to predict concentration profiles for unmeasured species. Predicted profiles were consistent with measured data. Thus, by also accounting for pressure effects, the new model provides a sound basis for modeling the industrial process. The allene-doped ethylene flame had a fuel equivalence ratio of 1.9 and feed gas composition of 0.5% allene, 18.9% C2H4, 30.9% O 2, and 49.7% Ar. It was operated at 20.00 ± 0.01 Torr with a burner surface gas velocity at 298 K of 62.5 cm/s. Mole fraction profiles were measured for 41 stable and radical species. Data from this allene-doped ethylene flame were compared to the data of Bhargava's (1997) nearly identical fuel-rich undoped ethylene flame. Addition of allene enhanced the production of phenyl and benzene, supporting the arguments that C3 species play a very important role in the formation of phenyl and benzene. Using the data and reaction path analysis, Bhargava's (1997) reaction set was improved. New rate constants were determined, incorrect reactions were removed, and new chemistry was added, improving many of the model predictions. Modeling suggested that the major reaction responsible for increased production of phenyl and benzene was 2C3H3 = phenyl +H. Identification and analysis of an important error in Bhargava's reaction set suggest that a reactive boundary condition at the burner surface may be necessary for improved modeling of this flame.

Subject Area

Chemical engineering|Chemistry|Analytical chemistry

Recommended Citation

Oulundsen, George Edward, "Molecular -beam mass spectrometry and modeling of a propylene /chlorine reactive flow and an ethylene flame doped with allene" (1999). Doctoral Dissertations Available from Proquest. AAI9950195.