Room Temperature Reaction of Ozone and Dimethyl Methylphosphonate (DMMP) on Alumina-Supported Iron Oxide

The reaction of dimethyl methylphosphonate (DMMP) with ozone on a reactive adsorbent, alumina-supported iron oxide, has been examined at room temperature. The surface oxidation reaction was found to follow the Langmuir−Hinshelwood mechanism, involving a surface adsorbed and activated DMMP molecule or fragment at a Lewis acid site and an active oxygen species on the surface formed from ozone. Carbon dioxide is the primary reaction product observed, and the amount formed was found to plateau as a function of ozone concentration after a concentration of approximately 300−400 ppm. The surface reaction with ozone on the 10 wt % Fe2O3/Al2O3 adsorbent generates approximately 2.7 times as much gas-phase carbon, in the form of CO2 and CO, as does the same surface in the absence of ozone, in the form of methanol. The ozone appears to increase the number of active sites for DMMP decomposition by liberating some of the reaction products from the surface and recycling the surface sites. The supported iron oxide material is a more effective reactive surface than alumina for the reaction with ozone primarily because of its greater facility for ozone decomposition. The gas-phase reaction between DMMP and O3 for the formation of CO2, while not the focus of the study, was found to be of fractional order in O3, indicating a multistep reaction mechanism.