Characterizations of platinum catalysts supported on Ce, Zr, Pr-oxides and formation of carbonate species in catalytic wet air oxidation of acetic acid

Abstract

Catalytic wet air oxidation (CWAO) of aqueous solution of acetic acid (78 mmol L −1) was carried out with pure oxygen (2 MPa) at 200 °C in a stirred batch reactor on platinum supported oxide catalysts (Pt/oxide, oxide = CeO 2, Zr 0.1Ce 0.9O 2, Zr 0.1(Ce 0.75Pr 0.25) 0.9O 2 and ZrO 2). Platinum was loaded on oxides by impregnation (5 wt%), and then the catalysts were reduced under H 2. Homogenous dispersions of 2–3 nm metal crystallites were obtained. The catalytic activity depended on the ability of the support to resist to the formation of carbonates. Ce(CO 3)OH species, determined by FT-IR and XRD, were rapidly formed during the CWAO reaction especially on mixed oxides. These carbonates were responsible to a drastic drop in catalytic performances. Amounts of carbonate species increase with the ability of the catalyst to transfer oxygen.