Exploring the high-temperature kinetics of diethyl carbonate (DEC) under pyrolysis and flame conditions

Abstract

To pursue insights into the high-temperature kinetics of diethyl carbonate (DEC), a potential clean oxygenated additive for diesel fuels, a systematical kinetic investigation was carried out in this work. Species mole fraction variations were recorded by a gas chromatography (GC) system during the pyrolysis of DEC in a flow reactor under three different pressures (30, 150 and 780Torr). And quantitative measurements were conducted for over thirty species in a fuel-rich (ϕ=1.5) premixed DEC/O2/argon flame using synchrotron vacuum ultraviolet photoionization mass spectrometry. Pressure-dependent rate coefficients for DEC unimolecular decompositions were obtained with RRKM/master equation calculations. A kinetic model for DEC high-temperature pyrolysis and combustion was developed employing the calculated kinetic parameters, which could well predict all available measurements. Model analysis revealed that a two-step molecular elimination pathway exclusively led to the fuel decomposition under pyrolysis conditions, while in the premixed flame the fuel was consumed mainly by hydrogen abstractions from the secondary carbon atoms. The pyrolysis and combustion behaviors of DEC were compared with those of dimethyl carbonate (DMC), a simpler homologue of DEC, under similar conditions. It was found that DEC was of less thermal stability during the pyrolysis and that C2 intermediates were of much higher concentrations in the DEC flame. Furthermore, it was found that DEC shared combustion characteristics with some other oxygenated fuels possessing specific common structural features.