TY - JOUR
T1 - Accurate and standard thermochemistry for oxygenated hydrocarbons: A case study of ethyl levulinate
AU - Ghosh, Manik Kumer
AU - Howard, Mícheál Séamus
AU - Dooley, Stephen
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This works was supported by the Future Fuels project supported by the Competitive Center Funding (CCF) program at King Abdullah University of Science and Technology (KAUST), Science Foundation Ireland and the Irish Centre for High-End Computing (ICHEC). We thank Dr. Branko Rusic for his assistance in reviewing the Active Thermochemical Tables.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
PY - 2018/7/24
Y1 - 2018/7/24
N2 - The enthalpies of formation are a critical fundamental parameter for the combustion modelling. The enthalpies of formation of the species of the high temperature combustion mechanism of the lignocellulosic biofuel, ethyl levulinate are determined by a number of methodologies. Chemical group additivity, atomization and isodesmic worked reactions are employed with total reaction energies computed from theory with the CBS-QB3, CBS-APNO, and G4MP2 methodologies. These calculations reveal that significant differences as high as 6.2 kcal/mol can be found between each method for the large oxygenated hydrocarbons that were tested. It is found that there is a lack of standard reference enthalpies of formation for liquid-fuel size oxygenated hydrocarbons for both molecules and radicals. In their absence, a benchmarking of the computational methodologies employed in this study to values available in the Active Thermochemical Tables for smaller oxygenated species is performed. The results show that the atomization methods performed at each separate theoretical method show mean absolute deviations against the benchmarking data set of between 0.4–0.7 kcal/mol for radicals, and 0.6–1.9 kcal/mol for molecules. By combining the data obtained with each individual method by unweighted averaging, mean absolute deviations of 0.3 and 0.5 kcal/mol for radicals and molecules can respectively result. However, the computed enthalpies of formation via the atomization procedure of larger species, of the ethyl levulinate system show variations of between 4.3–6.2 kcal/mol for molecules and 0.9–3.4 kcal/mol for radicals. As the values generated by the isodesmic reaction procedure show lower variations of 0.5–0.8 kcal/mol for radicals and 2.3–3.8 kcal/mol for molecules. Consequently, in the absence of more appropriate reference data to benchmark computational methodologies, this study recommends the use of isodesmic reactions executed at multiple theoretical methods for the determination of enthalpies of formation.
AB - The enthalpies of formation are a critical fundamental parameter for the combustion modelling. The enthalpies of formation of the species of the high temperature combustion mechanism of the lignocellulosic biofuel, ethyl levulinate are determined by a number of methodologies. Chemical group additivity, atomization and isodesmic worked reactions are employed with total reaction energies computed from theory with the CBS-QB3, CBS-APNO, and G4MP2 methodologies. These calculations reveal that significant differences as high as 6.2 kcal/mol can be found between each method for the large oxygenated hydrocarbons that were tested. It is found that there is a lack of standard reference enthalpies of formation for liquid-fuel size oxygenated hydrocarbons for both molecules and radicals. In their absence, a benchmarking of the computational methodologies employed in this study to values available in the Active Thermochemical Tables for smaller oxygenated species is performed. The results show that the atomization methods performed at each separate theoretical method show mean absolute deviations against the benchmarking data set of between 0.4–0.7 kcal/mol for radicals, and 0.6–1.9 kcal/mol for molecules. By combining the data obtained with each individual method by unweighted averaging, mean absolute deviations of 0.3 and 0.5 kcal/mol for radicals and molecules can respectively result. However, the computed enthalpies of formation via the atomization procedure of larger species, of the ethyl levulinate system show variations of between 4.3–6.2 kcal/mol for molecules and 0.9–3.4 kcal/mol for radicals. As the values generated by the isodesmic reaction procedure show lower variations of 0.5–0.8 kcal/mol for radicals and 2.3–3.8 kcal/mol for molecules. Consequently, in the absence of more appropriate reference data to benchmark computational methodologies, this study recommends the use of isodesmic reactions executed at multiple theoretical methods for the determination of enthalpies of formation.
UR - http://hdl.handle.net/10754/629781
UR - https://linkinghub.elsevier.com/retrieve/pii/S1540748918304462
UR - http://www.scopus.com/inward/record.url?scp=85050335928&partnerID=8YFLogxK
U2 - 10.1016/j.proci.2018.07.028
DO - 10.1016/j.proci.2018.07.028
M3 - Article
SN - 1540-7489
VL - 37
SP - 337
EP - 346
JO - Proceedings of the Combustion Institute
JF - Proceedings of the Combustion Institute
IS - 1
ER -