Grantee Research Project Results
1999 Progress Report: Kinetic and Mechanistic Studies of the Reactions of Hydroxyl Radical with the Chloroethenes over an Extended Temperature Range
EPA Grant Number: R826169Title: Kinetic and Mechanistic Studies of the Reactions of Hydroxyl Radical with the Chloroethenes over an Extended Temperature Range
Investigators: Taylor, Philip H.
Institution: University of Dayton
EPA Project Officer: Hahn, Intaek
Project Period: November 24, 1997 through November 23, 2000
Project Period Covered by this Report: November 24, 1998 through November 23, 1999
Project Amount: $356,702
RFA: Exploratory Research - Environmental Engineering (1997) RFA Text | Recipients Lists
Research Category: Safer Chemicals , Land and Waste Management
Objective:
The overall goal of this research is to determine the rates and mechanisms of OH reactions with the chloroethenes over an extended temperature range. The specific rate coefficients can be used to improve the design of hazardous waste incinerators with respect to these thermally stable products of incomplete combustion. Thermochemical data also will be determined under conditions when the rate of reverse dissociation is comparable with that of direct addition process and the chemically activated Cl elimination channel is negligibly slow. Specific goals of this research include: (1) the first absolute rate measurements of the reaction of OH with CH2=CCl2, cis-CHCl=CHCl, trans-CHCl=CHCl, CHCl=CCl2, and CCl2=CCl2 over an extended temperature range with determination of accurate Arrhenius or modified Arrhenius parameters; (2) determination of the relative importance of Cl elimination versus H atom abstraction at elevated temperatures; and (3) determination of the relative importance of Cl elimination versus adduct stabilization at lower temperatures.Progress Summary:
The experimental and modeling studies of OH reaction with C2Cl4 and C2HCl3 have been completed and submitted for publication. The experimental studies for OH reaction with trans-C2H2Cl2 also have been completed. Modeling of the data is in progress. Experimental studies of OH reaction with 1,1-C2H2Cl2 and C2H3Cl are in progress. For the completed reactions, significant accomplishments include the following: (1) adduct stabilization dominates the overall reaction at low temperatures and atmospheric pressures; (2) Cl elimination dominates the overall reaction at post-combustion temperatures (~1,000 K); (3) H atom abstraction is insignificant under post-combustion conditions. It is of minor importance under higher temperature flame conditions (2,000 K); and (4) the relative energy of the initial transition states (compared to the reactants) plays an important role in the room temperature reactivity of these compounds.Future Activities:
During the final year of the grant, we will obtain rate data for CH2=CHCl. We will focus particularly on data above 600 K, and determine whether the H-atom abstraction channel can be resolved from competing Cl-elimination channels. H atom abstraction data were not observable for CHCl=CCl2 and trans-CHCl=CHCl due to the rapid rate of Cl elimination. At elevated temperatures, we will use an alternative OH precursor (N2O/H2O mixtures) that allows measurements between 750 and 950 K. This approach is not possible with the other chlorinated ethenes due to their large absorption cross-sections at 193 nm. For CH2=CHCl and CH2=CCl2, we also will obtain data at lower reactor pressures to investigate falloff behavior that is predicted based on our QRRK/ab initio modeling results. Journal articles for the following reactions also will be prepared during the final year of the grant: OH + CH2=CHCl, OH + CH2=CCl2, and OH + trans-CHCl=CHCl. Experimental measurements for cis-CHCl=CHCl are not planned at this time.Journal Articles on this Report : 2 Displayed | Download in RIS Format
| Other project views: | All 6 publications | 2 publications in selected types | All 2 journal articles |
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Tichenor LB, Graham JL, Yamada T, Taylor PH. Kinetic and modeling studies of the reaction of hydroxyl radicals with tetrachloroethylene. Journal of Physical Chemistry A 2000;104(8):1700-1707. |
R826169 (1999) R826169 (Final) |
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Tichenor LB, El-Sinawi A, Yamada T, Taylor PH, Peng J, Hu X, Marshall P. Kinetic studies of the reaction of hydroxyl radicals with trichloroethylene and tetrachloroethylene. Chemosphere 2001;42(5-7):571-577 |
R826169 (1999) R826169 (Final) |
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Supplemental Keywords:
atmospheric chemistry, combustion chemistry, environmental engineering, exposure, air pollution., RFA, Scientific Discipline, Waste, Environmental Chemistry, Incineration/Combustion, Environmental Engineering, combustion contaminants, detailed chemical kinetics, toxic organic chemicals, high temperature reaction kinetics, hazardous waste incinerators, mechanistic study, hydroxyl radicals, laser induced flourescenceRelevant Websites:
http://udri.udayton.edu/enviroscience/Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.