Grantee Research Project Results

1999 Progress Report: Formation of Chlorinated PAHs in the Combustion and Thermal Processing of Chlorine Containing Materials

EPA Grant Number: R826167
Title: Formation of Chlorinated PAHs in the Combustion and Thermal Processing of Chlorine Containing Materials
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: $360,366
RFA: Exploratory Research - Environmental Engineering (1997) RFA Text |  Recipients Lists
Research Category: Safer Chemicals , Land and Waste Management

Objective:

Impending strict regulations of all combustion and thermal sources under the Clean Air Act Amendments, Resource Conservation and Recovery Act (RCRA), and U.S. Environmental Protection Agency's (EPA) Combustion Strategy will be based on calculated risk and the ability of the source to minimize emissions of harmful air pollutants. Previous research indicates that a potentially complex array of planar, chlorinated polycyclic aromatic hydrocarbons (PAHs) may be formed from thermal processing of chlorine-containing materials. The toxicity and endocrine-disrupting capabilities of these products are a major concern. There is insufficient information on the nature and origin of these pollutants to make scientifically defensible regulatory decisions. The origin and pathways of formation of these chemicals are the subjects of this study.

Previous research on molecular growth of chlorinated hydrocarbons (CHCs) indicates that C2 olefinic and acetylenic radical-molecule Cl atom displacement reactions may proceed more rapidly than the corresponding H atom displacement reactions. This finding, along with the resistance of CHCs to oxidation, suggests that PAH formation may be more facile in chlorine-containing systems than purely hydrocarbon systems. Thus, the central hypothesis to be tested is that CHCs are more prone to formation of PAHs than hydrocarbons.

Progress Summary:

Experimental Results. We have completed the construction of the Laser Photolysis/Photo-Ionization Time of Flight Mass Spectrometer (LP/PI-ToFMS) system. We also have tested the data acquisition system that synchronizes the photolysis laser pulse, ToF pulser, and ToF detector. We have achieved the required sensitivity for radical and product detection by reducing background noise and improving photo-ionization signal intensity. To further reduce background noise, a lithium fluoride (LiF) window was installed on the ion source (Ar lamp). The establishment of the data acquisition system and achievement of the required sensitivity were key issues to be accomplished for the second year of this project.

Modeling Results. We currently are focusing our research on the reaction of vinyl radical (C2H3) with the chlorinated ethylenes [C2HxCl(4-x) (0 x 3)]. Chemical activation theory is being used to model these reactions. Ab initio theory is being used to calculate thermodynamic properties of reactants, intermediate radicals, transition state (TS) compounds, and products. Gaussian 94 and Gaussian 98 computer codes are being used to perform the ab initio calculation on a Compaq alpha workstation recently purchased by the University of Dayton Research Institute (UDRI) and on an Origin 2000 supercomputer at the Ohio Supercomputer Center (OSC). Ab initio calculations have been completed for the following reactions:

1. C2H3 + C2H3Cl - and -addition (The -addition denotes C2H3 radical addition to the carbon that has two Hs. The -addition denotes C2H3 radical addition to the carbon that has H and Cl.)

2. C2H3 + CHClCHCl

3. C2H3 + C2HCl3 - and -addition (The -addition denotes C2H3 radical addition to the carbon that has H and Cl. The -addition denotes C2H3 radical addition to the carbon that has two Cls.)

4. C2H3 + C2Cl4

Chemically activated reaction systems have been analyzed for reactions (1) and (4) based on the thermodynamic properties calculated using ab initio theory.

Future Activities:

Experimental. Our primary goal for the third year of this program is to obtain kinetic data for reactant decay rates and product formation rates for vinyl (C2H3) radical addition to the chlorinated ethylenes [C2HxCl(4-x) (0 x 3)]. The experiment will be extended to chlorinated vinyl radicals [C2HxCl(3-x) (0 x 2)] addition to chlorinated ethylenes [C2HxCl(4-x) (0 x 3)] if time and resources permit.

Theoretical. Chemically activated reaction systems will be analyzed for reactions 3, 4, and 5 using newly calculated thermodynamic properties using ab initio theory.

Journal Articles:

No journal articles submitted with this report: View all 7 publications for this project

Supplemental Keywords:

combustion chemistry, environmental engineering, exposure, air pollution, free radicals., RFA, Scientific Discipline, Waste, Toxics, HAPS, Environmental Chemistry, Incineration/Combustion, Environmental Engineering, carcinogens, combustion contaminants, hazardous air pollutants, hydrocarbons, incineration, RCRA, hydrocarbon, mass spectrometry, chlorinated PAHs, EPA's Combustion Strategy, chemical contaminants, thermal processing, air pollution

Relevant Websites:

http://udri.udayton.edu/enviroscience/ Exit

Progress and Final Reports:

Original Abstract

1998

Final Report