465407 Highly Dispersed Metals on Metal Oxide Supports Via Reactive Deposition from Supercritical CO2
We have investigated the deposition of platinum and copper acetylacetonates from supercritical CO2 on both γ-alumina and anatase catalyst supports. A comparison of these materials with others of similar composition prepared by wet impregnation from methanol led to the observation that metal adsorption from CO2 is irreversible, while adsorption from methanol can be reversed. A potential explanation for this behavior is that a specific interaction between CO2 and protonated surface oxides results in surface bicarbonate groups, which in turn undergo ion exchange with the organometallic precursors, leaving the metal ions bound to carbonate sites on the surface. This mechanism should result in highly dispersed metal ions having strong interactions with the surface. During calcination and reduction, the carbonates decompose, leaving metal nanoparticles on the surface. The effect of reduction method and of temperature during the calcination and reduction processes on the both size and morphology of the particles formed will be discussed.
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