2-methylfuran pyrolysis: Gas-phase modelling and soot formation

Since the recent discoveries in the high efficiency production methods of 2,5-dimethylfuran (2,5-DMF) and 2-methylfuran (2-MF), and due to their good physicochemical properties, these alkylated furan derivatives have been highly considered as fuels or additives in gasoline and diesel engines. However, the cyclic structures of 2,5-DMF and 2-MF may make them effective soot precursors. We have recently studied the capacity of 2,5-DMF to form soot under different pyrolysis experimental conditions, in a flow reactor, and we now focus on the study of the capacity of 2-MF to form soot under the same conditions. In this way, a systematic investigation of the temperature and fuel concentration effects on the soot formed in the 2-MF pyrolysis was undertaken, in an atmospheric-pressure flow reactor, in the temperature range of 975-1475 K, and with 9000 and 18,000 ppm of 2-MF (inlet total carbon of 45,000 and 90,000 ppm, respectively). The increase in the soot yield is favoured by the rise in both the temperature and the inlet 2-MF concentration, while the gas yield decreases as the temperature increases without a noticeable influence of the inlet 2-MF concentration. A gas-phase chemical kinetic model was proposed to describe both the pyrolysis of 2-MF and 2,5-DMF. It was validated against the gas-phase data obtained in this work, as well as with a series of experimental data from literature including shock tube and flow reactors. Results show that 2-MF has a high capacity to form soot, and C4 species play a major role in the formation of intermediates that yield polycyclic aromatic hydrocarbons (PAH), well known as soot precursors. However, the soot yield in the 2-MF pyrolysis was found to be lower than that in the 2,5-DMF pyrolysis, mainly because, according to modelling results, during the 2,5-DMF pyrolysis the cyclopentadienyl radicals are highly formed, whose recombination yields directly naphthalene without any other intermediate.