GAS-PHASE PYROLYSIS OF DIETHYL METHYLPHOSPHONATE

Flow reactor pyrolysis studies of diethyl methylphosphonate (DEMP) in nitrogen have been conducted over the temperature range 802 to 907 K, to gain insight into decomposition mechanisms relevant to incineration of organophosphorus chemical warfare agents. Experiments were conduct ed in a quartz-lined turbulent flow reactor with residence times betwe en 15 and 125 ms. Two techniques are used to identify products: Fourie r-transform infrared (FTIR) spectroscopy for volatile compounds, and g as chromatography/mass spectrometry (GC/MS) preceded by derivatization for products trapped in a liquid-nitrogen bath. Ethylene, ethanol, et hyl methylphosphonate, and methylphosphonic acid were identified as pr oducts; ethylene, ethanol and DEMP were quantified using FTIR. The mea n ratio of ethylene to ethanol is 1.66. Rates of DEMP decomposition an d product formation are independent of loading and reactor diameter. T he temperature dependence of the overall DEMP decomposition rate const ant was found to be: k[s(-1)]=29 x 10(16) exp(- 59.2 [kcal.mole(-1)]/( R T)). Bond scission and ring transition state mechanisms can explain the formation of ethylene and ethanol from DEMP and ethyl methylphosph onate.