High-temperature pyrolysis of dimethyl ether in shock waves

The high-temperature pyrolysis of dimethyl ether (DME) was studied behind reflected shock waves using single-pulse (reaction time between 1.3 and 2.9 ms), time-resolved IR absorption (3.39 mu m), IR emission (4.24 mu m), and UV absorption (216 nm) methods. The studies were done using DME-Ar, DME-H-2-Ar, DME-CO-Ar, and DME-CH2O-Ar mixtures in the temperature range 900-1900 K at pressures in the range 0.83-2.9 atm. From a computer simulation, a 94-reaction mechanism that could explain all our data was constructed. The rate constant expressions of the following five reactions at high temperatures are discussed in detail: CH3OCH3 + M --> CH3O + CH3 + M, H + CH3OCH3 --> CH3OCH2 + H-2, CH3 + CH3OCH3 --> CH3OCH2 + CH4, CH3O + CO --> CH3 + CO2, CH2O + CH3 --> CHO + CH4. We found that in the pyrolysis of DME there is an extremely low tendency to form higher hydrocarbons at high temperatures. (C) 2000 by The Combustion Institute.