A Comprehensive Study Of N-heptane Low Temperature Oxidation

This work combines experimental,theoretical and model research methods,using a jet stirred reactor coupled with synchrotron radiation photoionization mass spectrometry,gas chromatography and Fourier infrared variation spectrometer for the low-temperature oxidation of nheptane in the temperature range of 550 – 800 K,equivalent ratio of 0.5.The low-temperature oxidation products with a residence time of 1 second are qualitatively and quantitatively processed.Based on the experimental results,the low-temperature oxidation process of n-heptane was systematically studied.The reaction rate of some reactions was updated with reference to previous work.The bimolecular reactions of ketohydroperoxide(KHP),heptene and cyclic ether were added to the kinetic model,including the third oxygenation reactions.The photoionization cross-sections of the main C7 oxygen-containing compounds were measured.Their mole fractions were calculated and added to the kinetic model.The new kinetic model was verified with multiple experimental results.The uncertainty of several reactions’ rates in the model was discussed.By adjusting the ratio of chain branching to chain diffusion reactions,the kinetic model was improved in predicting the two key species,oxygen and carbonyl-hydroperoxide.The effects of the second oxygenation reaction,the third oxygenation reaction and the decomposition rate of KHP on the ignition delay time were discussed.The results show that in the temperature range of 700 – 900 K,the lowtemperature ignition delay time is affected by the third oxygen addition reactions,and the second oxygen addition reaction and KHP decomposition reaction’s rate;in the temperature range of 900 – 1000 K,the intermediate temperature ignition delay time is affected by the second oxygen addition reaction and the KHP decomposition reaction rate;when the temperature is higher than 1000 K,the ignition delay time is almost unaffected by the effects of third oxygenation reactions,second oxygenation reactions and KHP decomposition reaction rate.On the basis of these works,a new insight into the low-temperature oxidation process of linear alkanes is proposed.