A theoretical and kinetic modelling study of free radical addition reactions to unsaturated C2, C3 and C5 hydrocarbons
MetadataShow full item record
This item's downloads: 14 (view details)
Radical addition to the double bond of an olefin is an important reaction class in combustion mechanism development. Addition reactions of free radicals to small alkenes (C2 – C3) have been studied here at high levels of theory. To develop detailed pyrolysis and oxidation mechanisms of larger alkenes, a series of theoretical studies have been carried out for Ḣ atom addition reactions to C4 – C5 alkenes at the Combustion Chemistry Centre (C3) at NUI Galway. As a further step of this systematic project, addition reactions of Ḣ atoms to dienes have been studied at similar levels of theory. From the perspective of Ḣ atom addition to 1,3-pentadiene, an ab initio and transition state theory (TST) study has been carried out for the reactions on the Ċ5H9 potential energy surface (PES) in this thesis, with the calculations of thermochemistry, high-pressure limiting and pressure-dependent rate constants. A chemical kinetic model describing reactions related to the Ċ5H9 PES was developed with thermochemistry and rate constants for Ḣ atom addition reactions, H-atom abstraction reactions by Ḣ atoms and other radicals (e.g. ĊH3, ȮH), and unimolecular decomposition reactions of related species. This model was then incorporated into AramcoMech3.0 to simulate experimental species concentration profiles available in the literature. The pressure-dependent rate constants calculated were compared to the literature results, with a difference of 40% in the partition function calculations at 300 K observed between this work and the literature data. This is due to the use of different density functional theory (DFT) methods for the hindered rotor treatment. To validate the uncertainties of rate constants that stem from the use of different electronic structure methods for the hindered-rotor treatment, the rotations of rotors that are newly formed from radical additions to C2/C3 unsaturated hydrocarbons were calculated using twelve DFT methods. For rotors formed by Ṙ + C2 alkenes/alkynes, the DFT results were also compared with DLPNO-CCSD(T)/CBS results. The uncertainties in the hindrance potential, rotational constant and partition function calculations stemmed from the use of different DFT methods for the internal rotor treatment and were discussed for the rotors formed by these radical addition reactions.
This item is available under the Attribution-NonCommercial-NoDerivs 3.0 Ireland. No item may be reproduced for commercial purposes. Please refer to the publisher's URL where this is made available, or to notes contained in the item itself. Other terms may apply.
The following license files are associated with this item: