Nitromethane pyrolysis and oxidation in a jet-stirred reactor: Experimental measurements, kinetic model validation and interpretation

Abstract

A jet-stirred reactor was used to investigate the nitromethane pyrolysis and oxidation characteristics over the temperature range of 675–1250 K at atmospheric pressure. Mole fraction profiles of reactants, intermediate hydrocarbon species and products were identified using gas chromatography and gas chromatography-mass spectrometer. Results show that the fuel begins to be destructed at around 725 K and completely vanishes at 900 K for all experimental conditions. Pyrolysis of nitromethane as a function of temperature shows three distinct regions for H2, CO and C2H4 species. In addition, a negative temperature coefficient (NTC) behavior of CO2 species for nitromethane oxidation was observed, which has never been reported previously. The NTC region of CO2 species extends with the increase of equivalence ratio. These measured data were then used to validate several recently developed models of nitromethane. Results show that the model of Mathieu et al. (Mathieu et al. Fuel 182(2016):597) predicts the measured data well at low temperature (below 900 K) for all conditions. However, at intermediate temperature Mathieu model predicted intermediated species and main products deviate noticeably from measured data. Detailed reaction pathway analysis was conducted to direct future model refinement. Results show that the deviation between model predictions and measurements at intermediate temperature may be attributed to the reactions that involve the H and OH radicals. Further comparisons of the sensitive reactions for H and OH formations from different literatures were conducted, and large deviations in rate constants among these reactions suggest the directions of future model refinement.