Thermochemical Kinetics of Pyrolysis and Oxidation of Biodiesel for Predictive Combustion Modeling
EMSL Project ID
40018
Abstract
The increasing sensitivity in the U.S. over the dependence on foreign sources of crude oil for energy production, as well as the need to limit the release of greenhouse gases into the atmosphere, is leading a push for alternatives to fossil fuels. One of the promising alternatives to conventional petroleum in the transportation sector is blended biodiesel fuel. Biodiesel is a mixture of several alkyl esters, produced by the transesterification of triglycerides from natural renewable sources (e.g., vegetable oils) with alcohols (usually methanol for biodiesel methyl esters). Commercial biodiesel in the U.S. and in Europe are principally made up of two large saturated esters, methyl palmitate (CH3OOC16H31) and methyl stearate (CH3OOC18H35), and three unsaturated esters, methyl oleate (CH3OOC18H33), methyl linoleate (CH3OOC18H31) and methyl linolenate (CH3OOC18H29). The clean and efficient utilization of these bio-fuels in diesel engines requires a deep understanding of the combustion processes. The oxygen content in biodiesel leads to a more complete combustion, resulting in the production of lower amounts of particulate pollutants than petro-diesel. However, experimental studies have demonstrated that the presence of unsaturated bonds in the ester chains promote soot formation. The reaction pathways leading to early CO2 release and soot reduction by the ester moiety are uncertain, and the opposite influence of double bonds has an unclear origin. These and other differences in the chemical makeup of biodiesel lead to a unique chemistry whose full implications for combustion are not entirely understood. Accurate rate constants for effective kinetics modeling of the biodiesel combustion processes are not available at present. This proposal seeks computational resources to develop a reliable and detailed atomic-level description of these processes, by using the most accurate quantum chemistry methods available. Thermochemistry and rate constants of combustion reactions will be computed from accurate bond dissociation energies and activation energies (and pre-exponential factors), respectively. Our aim will be to identify and characterize the most significant kinetic steps involved in biodiesel high temperature pyrolysis and low temperature oxidation. Our results aim to contribute to the understanding of such biodiesel combustion properties as low soot emission and early release of CO2.
Project Details
Project type
Exploratory Research
Start Date
2010-12-20
End Date
2011-12-25
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Oyeyemi VB, JA Keith, M Pavone, and EA Carter. 2012. "Insufficient Hartree?Fock Exchange in Hybrid DFT Functionals Produces Bent Alkynyl Radical Structures." Journal of Physical Chemistry Letters 3(3):289-293. doi:10.1021/jz201564g
Oyeyemi VB, M Pavone, and EA Carter. 2011. "Accurate Bond Energies of Hydrocarbons from Complete Basis Set Extrapolated Multi-Reference Singles and Doubles Configuration Interaction." Chemphyschem 12:3354-3364. doi:10.1002/cphc.201100447