Low Temperature Oxidation Characteristics of n-Heptane in Methane Atmosphere

Low temperature oxidation of n-heptane in the atmosphere of different methane concentrations(by mole fraction)at 500-750 K were investigated experimentally in an atmospheric jet-stirred reactor. The equivalence ratio and residence time were fixed at 0.5 and 1.4 s, respectively. Variations of mole fractions of important intermediate species with the increasing initial temperature during the processes were presented. The physical and chemical effects of methane on the low temperature oxidation of n-heptane and the chemical kinetic characteristics of the low temperature oxidation process of n-heptane were studied. The result shows that methane acts as an inert gas at low methane contents, and its physical effect is equivalent to that of nitrogen. When methane content reaches 70%, methane inhibits the low temperature oxidation of n-heptane through its chemical effect. Reaction path analysis shows that the low temperature oxidation of n-heptane is mainly related to the reaction path of oxygenated substances, and the subsequent oxidation will be dominated by the reactions of CO, olefins and oxygenated substances such as aldehydes and ethers. Methane mainly inhibits the n-heptane oxidation by competing with n-heptane for OH. The increase of methane content promotes the formation of CH3, which increases the mole fraction of methanol. © 2021, Editorial Office of the Transaction of CSICE. All right reserved.