Reaction kinetics of dimethyl ether. II: low-temperature oxidation in flow reactors

Dimethyl ether oxidation has been studied in a variable-pressure flow reactor over an initial reactor temperature range of 550-850 K, in the pressure range 12-18 atm, at equivalence ratios of 0.7 ≤ φ ≤ 4.2, with nitrogen diluent of approximately 98.5%. On-line extraction sampling in conjunction with FTIR, NDIR (for CO and CO₂), and electrochemical (for O₂) analyses were performed to quantify species at specific locations along the axis of the turbulent flow reactor. Product species concentrations were correlated against residence time (at constant inlet temperature) and against temperature (at fixed mean residence time) in the reactor. Formic acid was observed as a major intermediate of dimethyl ether oxidation at low temperatures. The experimental species-evolution profiles were compared to the predictions of a previously published detailed kinetic mechanism [1]. This mechanism did not predict the formation of formic acid. In the current study we have included chemistry leading to formic acid formation (and oxidation). This new chemistry is discussed and is able to reproduce the experimental observations with good accuracy. In addition, this model is able to reproduce low-temperature kinetic data obtained in a jet-stirred reactor [2] and the shock-tube results of Pfahl et al. [3].