Ruthenium and platinum catalysts supported on Ce, Zr, Pr-O mixed oxides prepared by soft chemistry for acetic acid wet air oxidation

Abstract

Sol–gel Zr0.1Ce0.9O2 and Zr0.1(Ce0.75Pr0.25)O2 mixed oxides and commercial pure ceria CeO2 displaying the fluorine type structure have been used as platinum or ruthenium catalysts’ supports for catalytic wet air oxidation of aqueous solution of acetic acid (78mmolL−1) chosen as a model molecule. These catalysts were prepared by conventional impregnation (5wt.%) from platinum and ruthenium precursor salts. A screening of catalysts in CWAO at 200°C under 2MPa of partial oxygen pressure was performed and reveals that the best platinum catalyst is supported on pure ceria displaying large surface area. The mineralization of acetic acid solution reached 90% after 3h of reaction on PtCe catalyst. For ruthenium catalysts, the highest conversion after 3h of reaction has been reached by the Ru/Zr-Ce-O system (M3h=88%). Ce(CO3)OH species, evidenced by FT-IR and XRD, were formed during the CWAO reaction essentially on well dispersed platinum catalysts supported on mixed oxides. These carbonates were responsible of a drastic drop in catalytic performances. These carbonates were responsible of a drastic drop in catalytic performances. This carbonatation phenomenon was directly linked to the oxygen storage capacity (OSC) of the catalysts. A moderate OSC is required: when it is too high, it induces an inhibition of catalysts.