Experimental and Chemical Kinetics Investigation of High-Temperature Combustion of Diisopropyl Methylphosphonate.

Due to the high toxicity of chemical warfare (CW) agents, laboratory experiments are carried out using CW surrogates. Diisopropyl Methylphosphonate (DIMP), an organophosphate compound (OPC), is a crucial CW surrogate that has a chemical structure like the deadly nerve agent Sarin (GB). In this work, high-temperature combustion of DIMP is studied in a shock tube to understand the kinetics of destruction of DIMP. Laser absorption spectroscopy was used to obtain carbon monoxide mole fraction time-histories during high-temperature combustion of DIMP. Since combustion involves complex mixing phenomena involving different fuel to oxidizer ratios, experiments were conducted at conditions relevant to a) pyrolysis of DIMP, b) oxidation of DIMP, and c) combustion of DIMP in the presence of other fuels. The performance of the state-of-the-art reaction mechanism from Lawrence Livermore National Lab (LLNL) was evaluated against the CO mole fraction time-histories obtained during high-temperature combustion of DIMP. It was found that the LLNL mechanism severely underpredicted CO mole fraction time-histories compared to the experimental data. A systematic approach to improve the mechanism was carried out by including improved thermochemical data, adding relevant sub-mechanism of combustion intermediates, evaluating important reaction rates from first principles using quantum chemical simulations, and using rates of analogous reactions from literature. The reaction mechanism compiled for DIMP using these rates significantly improved the prediction of CO time-histories during DIMP combustion. Reaction path analysis and sensitivity analysis were also conducted to understand the formation pathways of CO during DIMP combustion. The reaction mechanism developed herein will aid in designing, developing, and optimizing tailor-made explosives for countering weapons of mass destruction (c-WMD)