Experimental and kinetic modeling study of polycyclic aromatic hydrocarbon formation pathways in fuel-rich oxidation of 2-methylfuran using an atmospheric flow reactor

2-Methylfuran is one of promising biofuels that is expected to be an alternative fuel or fuel additive to conventional fuels for reducing greenhouse gas emissions from internal combustion engines. Although oxidation experiments under a wide range of conditions are required for a better understanding of 2-methylfuran combustion, the fuel-rich oxidation of 2-methylfuran has not been studied extensively. In this study, the fuel-rich oxidation of 2-methylfuran was investigated using an atmospheric flow reactor at temperatures of 1000–1350 K, equivalence ratios of 3.0–12.0, and residence times of 0.2–1.5 s. Chemical species such as the polycyclic aromatic hydrocarbons (PAHs) with one to six aromatic rings formed in the oxidation were sampled and quantified using gas chromatography mass spectrometry, while small intermediate products from C1 to C5 were quantified using gas chromatograph equipped with flame ionization detector. A kinetic model was developed by combining the existing reaction mechanisms for 2-methylfuran oxidation and PAH growth, which were constructed separately. The developed model was validated against the experimental results obtained in this study, showing that the simulated concentration profiles of the chemical species were in reasonable agreement with the measured data under the present experimental conditions. Kinetic analyses using the model were conducted to unravel the reaction pathways of PAHs as well as the main consumption pathways of 2-methylfuran. These results showed that 2-methylfuran underwent ring cleavage and CO/CH3CO removal, resulting in production of C2–C4 species. It was also found that the resonantly stabilized radicals, particularly the propargyl radical, were the key species responsible for PAH growth reactions, and the hydrogen-abstraction carbon-addition mechanism was important for the formation of several PAHs.