No abstract

Dimethyl Carbonate (DMC) is a carbonate ester that can be produced in an environmentfriendly way from methanol and CO2. DMC is one of the main components of the flammable electrolyte used in Li-ion batteries, and it can also be used as a diesel fuel additive. Studying the combustion chemistry of DMC can therefore improve the use of biofuels and help developing safer Li-ion batteries. The combustion chemistry of DMC has been investigated in a limited number of studies. The aim of this study was to complement the scarce data available for DMC combustion in the literature. Laminar flame speeds at 318 K, 363 K, and 463 K were measured for various equivalence ratios (ranging from 0.7 to 1.5) in a spherical vessel, greatly extending the range of conditions investigated. Shock tubes were used to measure time histories of CO and H2O using tunable laser absorption for the first time for DMC. Characteristic reaction times were also measured through OH* emission. Shock-tube spectroscopic measurements were performed under dilute conditions, at three equivalence ratios (fuel-lean, stoichiometric, and fuel-rich) between 1260 and 1660 K near 1.3±0.2 atm, and under pyrolysis conditions (98%+) ranging from 1230 to 2500 K near 1.3±0.2 atm. Laminar flame speed experiments were performed around atmospheric pressure. Detailed kinetics models from the literature were compared to the data, and it was found that none are capable of predicting the data over the entire range of conditions investigated. A numerical analysis was performed with the most accurate model, underlining the need to revisit at least 3 key reactions involving DMC.

The oxidation of iso-octane was studied in two different shock tubes by recording mole fraction time histories of CO and H2O at various equivalence ratios (0.5, 1.0, and 2.0) at around 1.5 atm, between 1320 and 1815 K. Mixtures were diluted in 99% inert gases. Results show that the induction delay time for both CO and H2O are particularly sensitive to the temperature and the equivalence ratio. The CO profiles for the fuel-lean and stoichiometric mixtures present a peak in CO formation, due to the oxidation of CO to CO2. This peak was not observed for the fuel rich mixture, where the CO profile reaches a plateau within the time frame investigated. For the water profiles, they all present a plateau after the main water formation process, although this plateau is still ascending for the fuel-lean and stoichiometric mixtures during the test time. Experimental results were compared with detailed kinetics mechanisms from the literature, the most recent one (Atef et al. Comb. Flame 2017, 178, 111–134) being in overall good agreement with the data except for the maximum CO mole fraction at the lowest temperatures investigated. A numerical analysis was conducted with this model to explain the results and to identify ways to improve the model.