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

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 degrees C in a stirred batch reactor on platinum supported oxide catalysts (Pt/oxide, oxide = CeO2, Zr0.1Ce0.9O2, Zr-0.1(Ce0.75Pr0.25)(0.9)O-2 and ZrO2). 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(CO3)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. (C) 2007 Elsevier B.V. All rights reserved.