Abstract
A natural kaolinite from Argentinean deposits, converted into metakaolin by thermal treatment at 823K and chemically modified, was used as a support for catalysts containing iso- and heteropolyanions (POMs and HPOMs) such as ammonium heptamolybdate (AHM) and ammonium Anderson phases [XMo6O24H6]3− [X(III)=Al, Co]. The catalytic performances were analyzed in the clean selective oxidation of diphenyl sulfide (DPS) with H2O2. The chemical modification included treatment in acid solution and functionalization with 3-(aminopropyl)trimethoxysilane (F). The characterization was carried out by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), FTIR and Raman spectroscopies. Textural properties were determined by N2 adsorption-desorption isotherms (BET method); surface acid properties (Brønsted and Lewis surface acid sites) were measured by FTIR of adsorbed pyridine.A noticeable increase of surface areas and chemical composition change of the support occurred by acid treatment. Functionalization with amino-siliceous agents yielded an appropriate surface for the adsorption of POMs and HPOMs. The system containing Mo presented conversions of diphenyl sulfide of around 90% and high selectivity to diphenyl sulfone near 95%.
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