Cool Flames! Radical Reactions in Biofuels and in the Atmosphere

Research output: ThesisDoctoral Thesis

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QualificationDoctor of Philosophy
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Original languageEnglish

Abstract

A novel apparatus for pulsed laser photolysis generation of radicals coupled with
laser induced
uorescence (LIF) detection of OH has been developed at the University
of York, enabling kinetic studies of atmospheric and combustion-relevant chemical
reactions.
Direct LIF detection was used to identify unambiguously OH as a product of O2 +
RCO reactions, for the rst time, where R = CH3CH2CH2, (CH3)2CH, (CH3)3C,
CH3CH2CH2CH2, (CH3)2CHCH2, and CH3CH2CH(CH3). Pressure- dependent (13 -
120 Torr) OH yields were determined by comparison of time-resolved OH LIF proles
with those obtained from the well-characterised CH3CO + O2 ! OH reaction.
Results not only illustrate the dependency of OH yield on chain length and degree
of branching within the R group, but also resolve a literature discrepancy for
CH3CH2CO + O2 .
OH produced from RCO + O2 was used as a spectroscopic marker to study the
kinetics of Cl + RCHO. This indirect method produced the rst values for Cl +
(CH3)2CHCH2CHO ((3.1 0.6) 10􀀀10 cm3 molecule􀀀1 s􀀀1) and CH3CH2CH(CH3)
CHO ((1.2 0.3) 10􀀀10 cm3 molecule􀀀1 s􀀀1) at 298 K, with results for other Cl
+ RCHO and OH + RCHO reactions agreeing well with previous literature.
Finally, the reactions of RC(O)O2 with HO2 were investigated at temperatures
between 293 and 400 K. Preliminary experiments in the absence of HO2 recorded OH
production from a previously unknown source, potentially RC(O)O2 + RC(O)O2.
OH production from RC(O)O2 + HO2, identied for the rst time when R =
CH3CH2, (CH3)2CH, (CH3)3C, (CH3)2CHCH2, and CH3CH2CH(CH3), demonstrates
that signicant OH production is a general feature of HO2 + RC(O)O2 reactions.

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