Quantitative Study of the Decomposition of Dimethyl Methylphosphonate (DMMP) on Metal Oxides at Room Temperature and Above

The adsorption and decomposition reactions of dimethyl methylphosphonate (DMMP) on a commercial γ-Al2O3, a γ-Al2O3-supported iron oxide, and a sol−gel-prepared alumina have been examined at temperatures from 25 to 400 °C. The capacities of these solids for the decomposition of DMMP have been measured, and the identities and amounts of the decomposition products determined over the entire temperature range. The alumina surfaces yield higher total amounts of decomposition products than the supported iron oxide material, with the sol−gel alumina showing very high activity. When corrected for surface area, however, the supported iron oxide material shows an activity equal to that of the γ-Al2O3 support. The sol−gel alumina shows a higher activity at all temperatures up to saturation of the surface, presumably because of the presence of transitional phases that yield more reactive surface sites. At 25 °C, the commercial γ-Al2O3 shows a total decomposition capacity of 117 μmol/g, the alumina-supported iron oxide material a capacity of 93 μmol/g, and the sol−gel alumina a capacity of 208 μmol/g. At 100 °C, these capacities increase by about a factor of 3, and at 200 °C and above, all of the materials show some capacity for sustained decomposition of DMMP.