Date of Award

Spring 1-1-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry & Biochemistry

First Advisor

Jessica P. Porterfield

Second Advisor

G. Barney. Ellison

Third Advisor

Mark R. Nimlos

Fourth Advisor

John W. Daily

Fifth Advisor

Veronica M. Bierbaum

Abstract

This thesis describes the thermal, unimolecular decomposition pathways of the following potential biofuels: cyclohexanone (C6H10=O), glycolaldehyde (HCOCH2OH), methyl acetate (CH3COOCH3), and methyl butanoate (CH3CH2CH2COOCH3) as well as many products of their decomposition. These fuels have been diluted in a buffer gas (less than 0.1% in He, Ne, Ar, or Kr) and decomposed in a heated micro-reactor. The micro-reactor is a resistively heated silicon carbide (SiC) tube that can be heated to temperatures of up to 1800 K; it is 2 - 3 cm long and 0.6 to 1 mm in diameter. Residence times in the tiny reactor are roughly 25 - 150 microseconds. As the gas mixture exits the reactor, it expands supersonically into a vacuum chamber (1 x 10−6 Torr), which effectively quenches any further chemistry. Mass data of the products are provided by both tunable synchrotron photoionization mass spectrometry (PIMS) conducted at Lawrence Berkeley National Laboratory’s Advanced Light Source, and by pulsed, 10.487 eV PIMS conducted at the University of Colorado. Vibrational spectra are collected utilizing matrix isolation infrared spectroscopy (IR). Attempts to validate computational results of pressure within the reactor are also discussed, in which X-ray fluorescence studies were conducted inside the reactor using Kr as a fluorescent tag. With internal temperature and pressure characterized, the micro-reactor will also be a useful tool in determining rate constants of decomposition reactions. The complementary diagnostics of PIMS and IR detect all of the atoms, metastables, and radicals that results from pyrolysis of these fuels. Chemical decomposition pathways are then constructed to justify the observed product distribution.

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