Low temperature partial oxidation of ethane and propane

This work describes gas-phase flow-reactor experiments and modeling results for ethane and propane pyrolysis and partial oxidation. The experiments were carried out at an ambient pressure of 0.8 atm and a residence time of ∼5s and 550-800°C. Addition of small amounts of oxygen decreased the onset of conversion by ∼75K. This shift is well-predicted for ethane, while for propane the shift was over-predicted. Flux and sensitivity analyses point out that these results are very sensitive to the reaction of alkyl radicals with molecular oxygen. This improved prediction of ethane+O2 system is likely due to the use of the well-characterized ethyl+O2 sub-mechanism. On the other hand, the kinetic information of the analogous propyl+O2 system used in the mechanism was less certain. Therefore, the potential energy surface (PES) for propyl+O2 system was re-calculated using a higher level of electronic structure theory, namely CBS-QB3. New reaction pathways/species were found and included. In addition to the more accurate and complete PES, thermodynamic properties of species were improved. These improvements have led to substantial changes in the high-pressure rate constants. After accounting for the pressure effects, we anticipate improved predictions for propane.