DECOMPOSITION OF AN ORGANOPHOSPHONATE COMPOUND (DIMETHYL METHYLPHOSPHONATE) ON THE NI(111) AND PD(111) SURFACES

The decomposition of a model organophosphonate compound, dimethyl methylphosphonate (DMMP), by Pd(111) and Ni(111) surfaces has been studied by using Auger spectroscopy (AES) and temperature-programmed reaction spectroscopy (TPRS). In both cases, in the absence of O2, thermal decomposition of DMMP occurs [Pd, below 300 K; Ni, below 340 K] based on the observation of desorption-limited H2 and CO evolution. Phosphorus is deposited on both Pd(111) and Ni(111) surfaces following the DMMP decomposition. Oxidation at 1075 K removes the surface phosphorus on Pd(111). On Ni(111), however, surface phosphorus cannot be removed by oxidation at 1075 K, nor is preoxidized Ni(111) active for phosphorus removal at 1075 K. By comparison with similar experiments on Mo(110), it appears that the early transition metals may be more suitable for the catalytic oxidation of organophosphonate compounds, on the basis of the lower temperature for sustained removal of surface phosphorus by oxygen on Mo(110) [900 K] compared to Pd(111) [1075 K]. © 1990 American Chemical Society.