Modeling the Negative Temperature Coefficient in the Low Temperature Oxidation of Propane

摘要

The oxidation and combustion of propane has been modeled for low temperature conditions, ranging from ca. 500K to 800K and pressures from a few Torr to 15 atm. The high pressure rate constants for the critical reactions were calculated using CBS ab initio and DFT techniques. With only a few minor adjustments to the theoretical rate constants, within the expected uncertainty of the calculations, excellent agreement is obtained between the model and three very different experimental data sets. The chain branching needed for the NTC comes from the isomerization of the propyl peroxy radical CH_3CH_2CH_2OO· to CH_2·CH_2CH_2OOH, with subsequent addition of O_2 to produce CH_2(O·)CH_2CHO + 2 OH·. A small amount of chain branching comes from propylhydroperoxide, C_3H_7OOH, dissociation.