1999 Highlights


[
Source and Control] [Transport and Transformation] [Monitoring and Source Attribution]


Source and Control

 

Fundamental Study on High Temperature Chemistry of Oxygenated Hydrocarbons as Alternate Motor Fuels and Additives Joseph W. Bozzelli, New Jersey Institute of Technology

The dimethyl ether radical CH3OC.H2 reaction with oxygen, O2, is shown to be chain propagating through reactions with barriers that are below initial ener-gies of reactants. Reaction paths and kinetics are determined by ab initio calculations (MP2/CBSq and G2) and compared with experiment. Calculated reac-tion paths explain the explosive nature of ethers relative to hydrocarbons.

Variable pressure reaction mechanisms for use in a NJIT modified pressure dependent Chemkin Code are developed for MTBE and for dimethyl ether combus-tion.

A Web site is created for graphical description and quantitative thermodynamic pathway analysis for MTBE oxidation and combustion.

 

Origin and Characteristics of Fine Soot Particles in Combustion Jack B. Howard, Massachusetts Institute of Technology

The scanning mobility particle sizing method applied to the measurement of soot particle size distributions in flames has been found to be suitable for measuring relative changes and to be faster than the collection of samples followed by electron microscopy.

The limited injection of oxygen into sooting flames can either increase or decrease the amount of soot formed depending on whether the temperature is relatively low or high, respectively. Further increasing the amount of oxygen injection reduced soot number concentration and eventually decreases the particle mean diameter.

Observed rates of soot formation under various conditions in a plug flow reactor and in premixed flames exhibit similar oscillations to those observed in the concentration of polycyclic aromatic hydrocarbons while the concentration of acetylene varies monotonically, consistent with the hypothesis that PAH are the main reactants for soot growth.

 

Computer-Generated Kinetic Models for PAH Formation William H. Green, Massachusetts Institute of Technology

Methods for computing individual PAH reaction rates have been developed and are being validated, and these calculations are being generalized into reaction family rate estimation rules. These calculations reveal that the pressure-dependence of PAH reactions in low pressure flames must be considered despite the large size of the molecules involved. This is very important since most of the detailed data are measured at low pressure, but the chief technological applications occur at high pressure (e.g. in diesel engines) where the rates and products will be very different from those at lower pressures.

 

Numerical Tools for Large-Scale Kinetic Models Paul I Barton and William H. Green, Massachusetts Institute of Technology

DAEPACK version 1.0 has been completed and the software is now available for academic and commercial licensing. DAEPACK enables legacy FORTRAN models (e.g., CHEMKIN) to be automatically integrated with any new numerical algorithms that may be developed. Some novel but preliminary theoretical results have been developed indicating the feasibility of developing deterministic global optimization algorithms for kinetic model reduction.

 

 

Transport and Transformation

 

Modeling and Analysis of the Evolution of the Size and Composition Distribution of Atmospheric Organic Aerosols Glen R. Cass, California Institute of Technology

A photochemical trajectory model has been applied to study the formation and transport of particulate matter in the atmosphere along air parcel trajectories crossing the Los Angeles basin. Model predictions are in good agreement with detailed measurements of particle size and bulk chemical composition and reveal the major emissions source types that contribute to the Los Angeles fine particle problem. Methods have been developed for correcting and displaying the massive amount of data taken on single particle size and chemical composition during the field experiments modeled. These single particle data are being aligned with the air quality model in ways that will permit comparisons to be made between measurements and model predictions at the single particle level.

 

Laboratory Studies of the Photochemistry of Organic Peroxides: Determination of the Photolysis Rate for Conditions Appropriate for Use in Urban and Regional Air Quality Models, Paul Wennberg, California Institute of Technology

Equipment required for the measurement of the peroxide cross section has been developed.

 

Kinetics and Thermochemistry of Primary Steps in Oxidation of Airborne Organic Compounds Lev N. Krasnoperov, New Jersey Institute of Technology

The experimental facility based on the combination of a Laser Photolysis-Transient UV-Vis Spectroscopy was modified and upgraded to incorporate a powerful excimer laser and a fast Gated ICCD camera. Initial experimental data on the temporal profiles of hydroxyl and cyclohexadienyl radicals are acquired. Several methods of indirect photolytic production of (substituted) cyclohexadienyl radicals for quantitative kinetics studies were modeled and evaluated. A direct photolytic precursor was suggested, the synthesis of the required precursor molecule (commercially unavailable) was designed and initiated.

 

Secondary Organic Aerosol: Yields, Formation Mechanisms, and Molecular Speciation John Seinfeld and Richard Flagan, California Institute of Technology

Initial experiments investigating the affect of relative humidity and temperature on SOA partitioning were performed, as well as a complete analysis of the cyclohexene-ozone dark reaction including both physical and chemical analysis of products was completed. Additionally, an investigation into the hygroscopic nature of Pasadena fine particulate matter was carried out with a TDMA and finally the development of a new, state of the art, indoor air quality environmental chamber was designed and completed.

 

Laboratory Studies of the Atmospheric Oxidation of Aromatic Hydrocarbons Mario J. Molina, Massachusetts Institute of Technology

Ion-molecule rate constants have been measured for the reactions of the toluene-OH adduct with O2+ as well as for the reactions of two organic peroxy radicals with SF6-. OH decays and adduct growth curves for the toluene-OH system have also been determined.

 

Kinetics, Reaction Path Analysis and Elementary Reaction Mechanism Development for Atmospheric Photochemical Oxidation of Aromatics and Oxygenated Aromatics Joseph Bozzelli, New Jersey Institute of Technology

A detailed reaction mechanism with microscopic reversibility and the associate thermodynamic database has been established for toluene atmospheric oxidation. Predictions of our kinetic modeling are in good agreement with the experimental results. An initial mechanism for styrene is developed. Bond energies for C--H bonds on styrene, fulvene, and other 'aromatic' like systems and on hydrocarbon esters are calculated to be slightly (2-5 kcal/mole) higher than literature estimates. Rate constants for HO2 addition to olefins increase (barriers decrease) with increased hydrocarbon substitution on the olefinic carbon.

 

 

Monitoring and Source Attribution

 

Development of Semiconductor-Based Adsorption-Modified Photosensitization (SAMP) Sensors for a Sensor-Array Device for the Monitoring of Organic Gases Barbara Kebbekus, New Jersey Institute of Technology and Vladimir Zaitsev, Moscow State University

Solid state CdS sensors coated with Rhodamine B dye have been made. A manifold to produce varying concentrations of vapor has been built, and is presently being upgraded. Initial testing of the sensors shows sensitivity to toluene at levels of 0 to 4 ppm.

 


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