Degradation of Methyl Paraoxon in the Presence of Mg2+-Al3+ Mixed Oxides

Al3+-Mg3+ mixed oxides were prepared by coprecipitation and characterized with scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDXRF), temperature programmed desorption of CO2 (CO2-TPD), and N-2 adsorption/desorption isotherms (BET and BJH methods). By increasing the MgO concentration up to 31.8% (w/w), X-ray diffraction (XRD) measurements suggested an incipient magnesium aluminate spinel (MgAl2O4) phase. However, the spinel crystalline structure was obtained only after calcination at 950 degrees C. These materials were tested as catalysts in the propanolysis reaction of methyl paraoxon. This reaction in the presence of the more efficient incipient MgAl2O4 spinel is of the order of 2.5 X 10(5)-fold faster than the spontaneous propanolysis reaction and results in the formation of a product that is structurally related to a family of flame retardants. The different products of propanolysis and hydrolysis were identified by electrospray ionization mass spectrometry (ESI(+)-MS), ESI(+)-MS/MS) and liquid chromatography mass spectrometry (LC-MS/MS).