Semester

Summer

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Fabien Goulay

Committee Co-Chair

Blake Mertz

Committee Member

Blake Mertz

Committee Member

Brian Popp

Committee Member

Terry Gullion

Committee Member

Earl Scime

Abstract

Resonantly stabilized radicals (RSRs) play an important role in combustion environments due to their high stability resulting from resonance. Many RSRs such as the propargyl, allyl, or benzyl radicals are precursors to the formation of polycyclic aromatic hydrocarbons (PAHs), which can aggregate to form soot. Due to their stability, these RSRs can accumulate in combustion environments in significant quantities. The primary way these radical species are consumed in flames or by reactions with other abundant radicals, by self-recombination of propargyl to form benzene, or in the form of other abundant radicals such as the hydroxyl radical. Experimentally determining the pathways for consumption of these radicals is necessary to better understand soot formation pathways. Product analysis is obtained for the C3H3 + OH reaction using a multiplexed photoionization time-of-flight mass spectrometry coupled to synchrotron radiation at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratories in Berkeley, California. Product analysis supports the production of m/z 56, with the predominant isotope formed being acrolein. Notably absent is the presence of propargyl alcohol, which indicates that the allylic form is the most favorable structure. Among the smaller radical exit pathways, the vinyl radical is produced in appreciable quantities, indicating that its coproduct, CO, is a major product of the reaction at higher temperatures. The study of kinetics for these reactions in-house requires proper experimental setup that can provide the necessary conditions such as pressure and temperature. For combustion reactions, higher experimental temperatures are necessary to emulate the conditions in a flame. To this end, a high-temperature fast flow reactor is constructed to provide the necessary conditions for the reaction. Pressure measurements were conducted to obtain the flow velocity, pressure, and temperature of the gas in the high-temperature flow past a standing normal shockwave. The standing normal shockwave is formed by increasing pressure downstream from the supersonic gas expansion to form a differential of pressure between the nozzle and flow cell. To verify the temperature extracted from the pressure measurements, the CN radical was used to determine the temperature of a gas through rotational spectroscopy. CN radicals were produced by pulsed laser photolysis (PLP) at 266 nm from ICN precursor and its concentration is monitored using laser-induced fluorescence (LIF) at an excitation wavelength range of 378 - 382 nm. The rotational spectrum is obtained and analyzed with the PGOPHER software to determine the gas temperature.

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