Direct and Indirect Determinations of Elementary Rate Constants: H+O2 Chain Branching; the Dehydration of tertiary-Butanol; the Retro Diels-Alder Reaction of Cyclohexene; the Dehydration of Isopropanol

Abstract

Due to growing environmental concern over the continued use of fossil fuels, methods to limit emissions and partially replace fossil fuel use with renewable biofuels are of considerable interest. Developing chemical kinetic models for the chemistry that affects combustion properties is important to understanding how new fuels affect combustion energy conversion processes in transportation devices. This thesis reports the experimental study of several important reactions (the H+O2 branching reaction, the key decomposition reactions of tertiary-butanol, the dehydration reaction of isopropanol, and the retro Diels-Alder reaction of cyclohexene) and develops robust analysis methods to estimate the absolute uncertainties of specific elementary rate constants derived from the experimental data. In the study of the above reactions, both a direct and indirect rate constant determination technique with associated uncertainty estimation methodologies are developed.

In the study of the decomposition reactions, a direct determination technique is applied to experimental data gathered in preparation of this thesis. In the case of the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, both of which are used as internal standards for relative rate studies (Herzler et al. 1997) and chemical thermometry (Rosado-Reyes et al. 2013) , analysis showed an ~20 K difference in the reaction rate between the reported results and the previous recommendations. In light of these discrepancies, an uncertainty estimation of previous recommendations illuminated an uncertainty of at least 20 K for the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, thus resolving the discrepancies.

The determination of the H+O2 branching reaction and decomposition reactions of isopropanol used an indirect determination technique. The uncertainty of the H+O2 branching reaction rate is shown to be underestimated by previous analysis (Hong et al. 2011, Turányi, et al. 2012), and the dehydration reaction of isopropanol is shown to be four times faster than theoretical predictions. Analyses of uncertainties for these reactions show that a linearized local sensitivity analysis does not completely capture uncertainties.

Appendix B in this thesis includes additional work conducted during the preparation of this thesis, namely the measurement of derived cetane numbers for jet fuel surrogates.