Surface residues and decomposition of liquid and vapor diisopropyl methyl phosphonate (DIMP) interacting with metal oxides

Diisopropyl Methyl Phosphonate (DIMP) is a common non-toxic surrogate for chemical warfare agents (CWAs) suitable for laboratory studies of their decomposition mechanisms. The fate of DIMP when it comes in contact with different heated surfaces is of interest because similar interactions involving CWAs and solids can occur in many practical scenarios. Oxides of aluminum, magnesium, iron, copper, and silicon are common components in soil and construction materials; they can also be generated as products of the combustion of energetic formulations. Respectively, their interactions with both liquid and vapor-phase DIMP need to be quantified and understood. This study investigates experimentally how these oxides adsorb and decompose DIMP. Experiments with vapor-phase DIMP used a gas flow reactor at 200 °C. Experiments with liquid DIMP were performed using a thermogravimetric analyzer with temperatures of up to 350 °C. Infrared spectroscopy served to characterize decomposition products on the surface of the exposed oxides. Findings show that DIMP vapors decomposed most effectively when interacting with calcined MgO. Correlations are found between the effectiveness of decomposition of DIMP vapors and residual masses left on the oxide surfaces by both liquid and vapor DIMP. Reaction mechanisms involving the conversion of DIMP to its surface residues on different oxide surfaces are proposed based on the present results.